linux/arch/x86/xen/p2m.c

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/*
* Xen leaves the responsibility for maintaining p2m mappings to the
* guests themselves, but it must also access and update the p2m array
* during suspend/resume when all the pages are reallocated.
*
* The p2m table is logically a flat array, but we implement it as a
* three-level tree to allow the address space to be sparse.
*
* Xen
* |
* p2m_top p2m_top_mfn
* / \ / \
* p2m_mid p2m_mid p2m_mid_mfn p2m_mid_mfn
* / \ / \ / /
* p2m p2m p2m p2m p2m p2m p2m ...
*
* The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.
*
* The p2m_top and p2m_top_mfn levels are limited to 1 page, so the
* maximum representable pseudo-physical address space is:
* P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages
*
* P2M_PER_PAGE depends on the architecture, as a mfn is always
* unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to
* 512 and 1024 entries respectively.
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
*
* In short, these structures contain the Machine Frame Number (MFN) of the PFN.
*
* However not all entries are filled with MFNs. Specifically for all other
* leaf entries, or for the top root, or middle one, for which there is a void
* entry, we assume it is "missing". So (for example)
* pfn_to_mfn(0x90909090)=INVALID_P2M_ENTRY.
*
* We also have the possibility of setting 1-1 mappings on certain regions, so
* that:
* pfn_to_mfn(0xc0000)=0xc0000
*
* The benefit of this is, that we can assume for non-RAM regions (think
* PCI BARs, or ACPI spaces), we can create mappings easily b/c we
* get the PFN value to match the MFN.
*
* For this to work efficiently we have one new page p2m_identity and
* allocate (via reserved_brk) any other pages we need to cover the sides
* (1GB or 4MB boundary violations). All entries in p2m_identity are set to
* INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs,
* no other fancy value).
*
* On lookup we spot that the entry points to p2m_identity and return the
* identity value instead of dereferencing and returning INVALID_P2M_ENTRY.
* If the entry points to an allocated page, we just proceed as before and
* return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in
* appropriate functions (pfn_to_mfn).
*
* The reason for having the IDENTITY_FRAME_BIT instead of just returning the
* PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a
* non-identity pfn. To protect ourselves against we elect to set (and get) the
* IDENTITY_FRAME_BIT on all identity mapped PFNs.
*
* This simplistic diagram is used to explain the more subtle piece of code.
* There is also a digram of the P2M at the end that can help.
* Imagine your E820 looking as so:
*
* 1GB 2GB
* /-------------------+---------\/----\ /----------\ /---+-----\
* | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM |
* \-------------------+---------/\----/ \----------/ \---+-----/
* ^- 1029MB ^- 2001MB
*
* [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100),
* 2048MB = 524288 (0x80000)]
*
* And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB
* is actually not present (would have to kick the balloon driver to put it in).
*
* When we are told to set the PFNs for identity mapping (see patch: "xen/setup:
* Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start
* of the PFN and the end PFN (263424 and 512256 respectively). The first step
* is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page
* covers 512^2 of page estate (1GB) and in case the start or end PFN is not
* aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn
* to end pfn. We reserve_brk top leaf pages if they are missing (means they
* point to p2m_mid_missing).
*
* With the E820 example above, 263424 is not 1GB aligned so we allocate a
* reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000.
* Each entry in the allocate page is "missing" (points to p2m_missing).
*
* Next stage is to determine if we need to do a more granular boundary check
* on the 4MB (or 2MB depending on architecture) off the start and end pfn's.
* We check if the start pfn and end pfn violate that boundary check, and if
* so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer
* granularity of setting which PFNs are missing and which ones are identity.
* In our example 263424 and 512256 both fail the check so we reserve_brk two
* pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing"
* values) and assign them to p2m[1][2] and p2m[1][488] respectively.
*
* At this point we would at minimum reserve_brk one page, but could be up to
* three. Each call to set_phys_range_identity has at maximum a three page
* cost. If we were to query the P2M at this stage, all those entries from
* start PFN through end PFN (so 1029MB -> 2001MB) would return
* INVALID_P2M_ENTRY ("missing").
*
* The next step is to walk from the start pfn to the end pfn setting
* the IDENTITY_FRAME_BIT on each PFN. This is done in set_phys_range_identity.
* If we find that the middle leaf is pointing to p2m_missing we can swap it
* over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this
* point we do not need to worry about boundary aligment (so no need to
* reserve_brk a middle page, figure out which PFNs are "missing" and which
* ones are identity), as that has been done earlier. If we find that the
* middle leaf is not occupied by p2m_identity or p2m_missing, we dereference
* that page (which covers 512 PFNs) and set the appropriate PFN with
* IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we
* set from p2m[1][2][256->511] and p2m[1][488][0->256] with
* IDENTITY_FRAME_BIT set.
*
* All other regions that are void (or not filled) either point to p2m_missing
* (considered missing) or have the default value of INVALID_P2M_ENTRY (also
* considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511]
* contain the INVALID_P2M_ENTRY value and are considered "missing."
*
* This is what the p2m ends up looking (for the E820 above) with this
* fabulous drawing:
*
* p2m /--------------\
* /-----\ | &mfn_list[0],| /-----------------\
* | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. |
* |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] |
* | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] |
* |-----| \ | [p2m_identity]+\\ | .... |
* | 2 |--\ \-------------------->| ... | \\ \----------------/
* |-----| \ \---------------/ \\
* | 3 |\ \ \\ p2m_identity
* |-----| \ \-------------------->/---------------\ /-----------------\
* | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... |
* \-----/ / | [p2m_identity]+-->| ..., ~0 |
* / /---------------\ | .... | \-----------------/
* / | IDENTITY[@0] | /-+-[x], ~0, ~0.. |
* / | IDENTITY[@256]|<----/ \---------------/
* / | ~0, ~0, .... |
* | \---------------/
* |
* p2m_mid_missing p2m_missing
* /-----------------\ /------------\
* | [p2m_missing] +---->| ~0, ~0, ~0 |
* | [p2m_missing] +---->| ..., ~0 |
* \-----------------/ \------------/
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
*
* where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT)
*/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/hash.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <asm/cache.h>
#include <asm/setup.h>
#include <asm/xen/page.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>
#include <xen/grant_table.h>
#include "multicalls.h"
#include "xen-ops.h"
static void __init m2p_override_init(void);
unsigned long xen_max_p2m_pfn __read_mostly;
#define P2M_PER_PAGE (PAGE_SIZE / sizeof(unsigned long))
#define P2M_MID_PER_PAGE (PAGE_SIZE / sizeof(unsigned long *))
#define P2M_TOP_PER_PAGE (PAGE_SIZE / sizeof(unsigned long **))
#define MAX_P2M_PFN (P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE)
/* Placeholders for holes in the address space */
static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE);
static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE);
static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_missing_mfn, P2M_MID_PER_PAGE);
static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE);
static RESERVE_BRK_ARRAY(unsigned long, p2m_top_mfn, P2M_TOP_PER_PAGE);
static RESERVE_BRK_ARRAY(unsigned long *, p2m_top_mfn_p, P2M_TOP_PER_PAGE);
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
static RESERVE_BRK_ARRAY(unsigned long, p2m_identity, P2M_PER_PAGE);
RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
/* We might hit two boundary violations at the start and end, at max each
* boundary violation will require three middle nodes. */
RESERVE_BRK(p2m_mid_identity, PAGE_SIZE * 2 * 3);
static inline unsigned p2m_top_index(unsigned long pfn)
{
BUG_ON(pfn >= MAX_P2M_PFN);
return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);
}
static inline unsigned p2m_mid_index(unsigned long pfn)
{
return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;
}
static inline unsigned p2m_index(unsigned long pfn)
{
return pfn % P2M_PER_PAGE;
}
static void p2m_top_init(unsigned long ***top)
{
unsigned i;
for (i = 0; i < P2M_TOP_PER_PAGE; i++)
top[i] = p2m_mid_missing;
}
static void p2m_top_mfn_init(unsigned long *top)
{
unsigned i;
for (i = 0; i < P2M_TOP_PER_PAGE; i++)
top[i] = virt_to_mfn(p2m_mid_missing_mfn);
}
static void p2m_top_mfn_p_init(unsigned long **top)
{
unsigned i;
for (i = 0; i < P2M_TOP_PER_PAGE; i++)
top[i] = p2m_mid_missing_mfn;
}
static void p2m_mid_init(unsigned long **mid)
{
unsigned i;
for (i = 0; i < P2M_MID_PER_PAGE; i++)
mid[i] = p2m_missing;
}
static void p2m_mid_mfn_init(unsigned long *mid)
{
unsigned i;
for (i = 0; i < P2M_MID_PER_PAGE; i++)
mid[i] = virt_to_mfn(p2m_missing);
}
static void p2m_init(unsigned long *p2m)
{
unsigned i;
for (i = 0; i < P2M_MID_PER_PAGE; i++)
p2m[i] = INVALID_P2M_ENTRY;
}
/*
* Build the parallel p2m_top_mfn and p2m_mid_mfn structures
*
* This is called both at boot time, and after resuming from suspend:
* - At boot time we're called very early, and must use extend_brk()
* to allocate memory.
*
* - After resume we're called from within stop_machine, but the mfn
* tree should alreay be completely allocated.
*/
void __ref xen_build_mfn_list_list(void)
{
unsigned long pfn;
/* Pre-initialize p2m_top_mfn to be completely missing */
if (p2m_top_mfn == NULL) {
p2m_mid_missing_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_mfn_init(p2m_mid_missing_mfn);
p2m_top_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_top_mfn_p_init(p2m_top_mfn_p);
p2m_top_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_top_mfn_init(p2m_top_mfn);
} else {
/* Reinitialise, mfn's all change after migration */
p2m_mid_mfn_init(p2m_mid_missing_mfn);
}
for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) {
unsigned topidx = p2m_top_index(pfn);
unsigned mididx = p2m_mid_index(pfn);
unsigned long **mid;
unsigned long *mid_mfn_p;
mid = p2m_top[topidx];
mid_mfn_p = p2m_top_mfn_p[topidx];
/* Don't bother allocating any mfn mid levels if
* they're just missing, just update the stored mfn,
* since all could have changed over a migrate.
*/
if (mid == p2m_mid_missing) {
BUG_ON(mididx);
BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;
continue;
}
if (mid_mfn_p == p2m_mid_missing_mfn) {
/*
* XXX boot-time only! We should never find
* missing parts of the mfn tree after
* runtime. extend_brk() will BUG if we call
* it too late.
*/
mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_mfn_init(mid_mfn_p);
p2m_top_mfn_p[topidx] = mid_mfn_p;
}
p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]);
}
}
void xen_setup_mfn_list_list(void)
{
BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
virt_to_mfn(p2m_top_mfn);
HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn;
}
/* Set up p2m_top to point to the domain-builder provided p2m pages */
void __init xen_build_dynamic_phys_to_machine(void)
{
unsigned long *mfn_list = (unsigned long *)xen_start_info->mfn_list;
unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
unsigned long pfn;
xen_max_p2m_pfn = max_pfn;
p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_init(p2m_missing);
p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_init(p2m_mid_missing);
p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_top_init(p2m_top);
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
p2m_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_init(p2m_identity);
/*
* The domain builder gives us a pre-constructed p2m array in
* mfn_list for all the pages initially given to us, so we just
* need to graft that into our tree structure.
*/
for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) {
unsigned topidx = p2m_top_index(pfn);
unsigned mididx = p2m_mid_index(pfn);
if (p2m_top[topidx] == p2m_mid_missing) {
unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_init(mid);
p2m_top[topidx] = mid;
}
xen: p2m: correctly initialize partial p2m leaf After changing the p2m mapping to a tree by commit 58e05027b530ff081ecea68e38de8d59db8f87e0 xen: convert p2m to a 3 level tree and trying to boot a DomU with 615MB of memory, the following crash was observed in the dump: kernel direct mapping tables up to 26f00000 @ 1ec4000-1fff000 BUG: unable to handle kernel NULL pointer dereference at (null) IP: [<c0107397>] xen_set_pte+0x27/0x60 *pdpt = 0000000000000000 *pde = 0000000000000000 Adding further debug statements showed that when trying to set up pfn=0x26700 the returned mapping was invalid. pfn=0x266ff calling set_pte(0xc1fe77f8, 0x6b3003) pfn=0x26700 calling set_pte(0xc1fe7800, 0x3) Although the last_pfn obtained from the startup info is 0x26700, which should in turn not be hit, the additional 8MB which are added as extra memory normally seem to be ok. This lead to looking into the initial p2m tree construction, which uses the smaller value and assuming that there is other code handling the extra memory. When the p2m tree is set up, the leaves are directly pointed to the array which the domain builder set up. But if the mapping is not on a boundary that fits into one p2m page, this will result in the last leaf being only partially valid. And as the invalid entries are not initialized in that case, things go badly wrong. I am trying to fix that by checking whether the current leaf is a complete map and if not, allocate a completely new page and copy only the valid pointers there. This may not be the most efficient or elegant solution, but at least it seems to allow me booting DomUs with memory assignments all over the range. BugLink: http://bugs.launchpad.net/bugs/686692 [v2: Redid a bit of commit wording and fixed a compile warning] Signed-off-by: Stefan Bader <stefan.bader@canonical.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-20 14:38:23 +00:00
/*
* As long as the mfn_list has enough entries to completely
* fill a p2m page, pointing into the array is ok. But if
* not the entries beyond the last pfn will be undefined.
*/
if (unlikely(pfn + P2M_PER_PAGE > max_pfn)) {
unsigned long p2midx;
p2midx = max_pfn % P2M_PER_PAGE;
for ( ; p2midx < P2M_PER_PAGE; p2midx++)
mfn_list[pfn + p2midx] = INVALID_P2M_ENTRY;
}
p2m_top[topidx][mididx] = &mfn_list[pfn];
}
m2p_override_init();
}
xen/p2m: Add logic to revector a P2M tree to use __va leafs. During bootup Xen supplies us with a P2M array. It sticks it right after the ramdisk, as can be seen with a 128GB PV guest: (certain parts removed for clarity): xc_dom_build_image: called xc_dom_alloc_segment: kernel : 0xffffffff81000000 -> 0xffffffff81e43000 (pfn 0x1000 + 0xe43 pages) xc_dom_pfn_to_ptr: domU mapping: pfn 0x1000+0xe43 at 0x7f097d8bf000 xc_dom_alloc_segment: ramdisk : 0xffffffff81e43000 -> 0xffffffff925c7000 (pfn 0x1e43 + 0x10784 pages) xc_dom_pfn_to_ptr: domU mapping: pfn 0x1e43+0x10784 at 0x7f0952dd2000 xc_dom_alloc_segment: phys2mach : 0xffffffff925c7000 -> 0xffffffffa25c7000 (pfn 0x125c7 + 0x10000 pages) xc_dom_pfn_to_ptr: domU mapping: pfn 0x125c7+0x10000 at 0x7f0942dd2000 xc_dom_alloc_page : start info : 0xffffffffa25c7000 (pfn 0x225c7) xc_dom_alloc_page : xenstore : 0xffffffffa25c8000 (pfn 0x225c8) xc_dom_alloc_page : console : 0xffffffffa25c9000 (pfn 0x225c9) nr_page_tables: 0x0000ffffffffffff/48: 0xffff000000000000 -> 0xffffffffffffffff, 1 table(s) nr_page_tables: 0x0000007fffffffff/39: 0xffffff8000000000 -> 0xffffffffffffffff, 1 table(s) nr_page_tables: 0x000000003fffffff/30: 0xffffffff80000000 -> 0xffffffffbfffffff, 1 table(s) nr_page_tables: 0x00000000001fffff/21: 0xffffffff80000000 -> 0xffffffffa27fffff, 276 table(s) xc_dom_alloc_segment: page tables : 0xffffffffa25ca000 -> 0xffffffffa26e1000 (pfn 0x225ca + 0x117 pages) xc_dom_pfn_to_ptr: domU mapping: pfn 0x225ca+0x117 at 0x7f097d7a8000 xc_dom_alloc_page : boot stack : 0xffffffffa26e1000 (pfn 0x226e1) xc_dom_build_image : virt_alloc_end : 0xffffffffa26e2000 xc_dom_build_image : virt_pgtab_end : 0xffffffffa2800000 So the physical memory and virtual (using __START_KERNEL_map addresses) layout looks as so: phys __ka /------------\ /-------------------\ | 0 | empty | 0xffffffff80000000| | .. | | .. | | 16MB | <= kernel starts | 0xffffffff81000000| | .. | | | | 30MB | <= kernel ends => | 0xffffffff81e43000| | .. | & ramdisk starts | .. | | 293MB | <= ramdisk ends=> | 0xffffffff925c7000| | .. | & P2M starts | .. | | .. | | .. | | 549MB | <= P2M ends => | 0xffffffffa25c7000| | .. | start_info | 0xffffffffa25c7000| | .. | xenstore | 0xffffffffa25c8000| | .. | cosole | 0xffffffffa25c9000| | 549MB | <= page tables => | 0xffffffffa25ca000| | .. | | | | 550MB | <= PGT end => | 0xffffffffa26e1000| | .. | boot stack | | \------------/ \-------------------/ As can be seen, the ramdisk, P2M and pagetables are taking a bit of __ka addresses space. Which is a problem since the MODULES_VADDR starts at 0xffffffffa0000000 - and P2M sits right in there! This results during bootup with the inability to load modules, with this error: ------------[ cut here ]------------ WARNING: at /home/konrad/ssd/linux/mm/vmalloc.c:106 vmap_page_range_noflush+0x2d9/0x370() Call Trace: [<ffffffff810719fa>] warn_slowpath_common+0x7a/0xb0 [<ffffffff81030279>] ? __raw_callee_save_xen_pmd_val+0x11/0x1e [<ffffffff81071a45>] warn_slowpath_null+0x15/0x20 [<ffffffff81130b89>] vmap_page_range_noflush+0x2d9/0x370 [<ffffffff81130c4d>] map_vm_area+0x2d/0x50 [<ffffffff811326d0>] __vmalloc_node_range+0x160/0x250 [<ffffffff810c5369>] ? module_alloc_update_bounds+0x19/0x80 [<ffffffff810c6186>] ? load_module+0x66/0x19c0 [<ffffffff8105cadc>] module_alloc+0x5c/0x60 [<ffffffff810c5369>] ? module_alloc_update_bounds+0x19/0x80 [<ffffffff810c5369>] module_alloc_update_bounds+0x19/0x80 [<ffffffff810c70c3>] load_module+0xfa3/0x19c0 [<ffffffff812491f6>] ? security_file_permission+0x86/0x90 [<ffffffff810c7b3a>] sys_init_module+0x5a/0x220 [<ffffffff815ce339>] system_call_fastpath+0x16/0x1b ---[ end trace fd8f7704fdea0291 ]--- vmalloc: allocation failure, allocated 16384 of 20480 bytes modprobe: page allocation failure: order:0, mode:0xd2 Since the __va and __ka are 1:1 up to MODULES_VADDR and cleanup_highmap rids __ka of the ramdisk mapping, what we want to do is similar - get rid of the P2M in the __ka address space. There are two ways of fixing this: 1) All P2M lookups instead of using the __ka address would use the __va address. This means we can safely erase from __ka space the PMD pointers that point to the PFNs for P2M array and be OK. 2). Allocate a new array, copy the existing P2M into it, revector the P2M tree to use that, and return the old P2M to the memory allocate. This has the advantage that it sets the stage for using XEN_ELF_NOTE_INIT_P2M feature. That feature allows us to set the exact virtual address space we want for the P2M - and allows us to boot as initial domain on large machines. So we pick option 2). This patch only lays the groundwork in the P2M code. The patch that modifies the MMU is called "xen/mmu: Copy and revector the P2M tree." Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-07-19 17:52:29 +00:00
#ifdef CONFIG_X86_64
#include <linux/bootmem.h>
unsigned long __init xen_revector_p2m_tree(void)
{
unsigned long va_start;
unsigned long va_end;
unsigned long pfn;
unsigned long *mfn_list = NULL;
unsigned long size;
va_start = xen_start_info->mfn_list;
/*We copy in increments of P2M_PER_PAGE * sizeof(unsigned long),
* so make sure it is rounded up to that */
size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
va_end = va_start + size;
/* If we were revectored already, don't do it again. */
if (va_start <= __START_KERNEL_map && va_start >= __PAGE_OFFSET)
return 0;
mfn_list = alloc_bootmem_align(size, PAGE_SIZE);
if (!mfn_list) {
pr_warn("Could not allocate space for a new P2M tree!\n");
return xen_start_info->mfn_list;
}
/* Fill it out with INVALID_P2M_ENTRY value */
memset(mfn_list, 0xFF, size);
for (pfn = 0; pfn < ALIGN(MAX_DOMAIN_PAGES, P2M_PER_PAGE); pfn += P2M_PER_PAGE) {
unsigned topidx = p2m_top_index(pfn);
unsigned mididx;
unsigned long *mid_p;
if (!p2m_top[topidx])
continue;
if (p2m_top[topidx] == p2m_mid_missing)
continue;
mididx = p2m_mid_index(pfn);
mid_p = p2m_top[topidx][mididx];
if (!mid_p)
continue;
if ((mid_p == p2m_missing) || (mid_p == p2m_identity))
continue;
xen/p2m: Add logic to revector a P2M tree to use __va leafs. During bootup Xen supplies us with a P2M array. It sticks it right after the ramdisk, as can be seen with a 128GB PV guest: (certain parts removed for clarity): xc_dom_build_image: called xc_dom_alloc_segment: kernel : 0xffffffff81000000 -> 0xffffffff81e43000 (pfn 0x1000 + 0xe43 pages) xc_dom_pfn_to_ptr: domU mapping: pfn 0x1000+0xe43 at 0x7f097d8bf000 xc_dom_alloc_segment: ramdisk : 0xffffffff81e43000 -> 0xffffffff925c7000 (pfn 0x1e43 + 0x10784 pages) xc_dom_pfn_to_ptr: domU mapping: pfn 0x1e43+0x10784 at 0x7f0952dd2000 xc_dom_alloc_segment: phys2mach : 0xffffffff925c7000 -> 0xffffffffa25c7000 (pfn 0x125c7 + 0x10000 pages) xc_dom_pfn_to_ptr: domU mapping: pfn 0x125c7+0x10000 at 0x7f0942dd2000 xc_dom_alloc_page : start info : 0xffffffffa25c7000 (pfn 0x225c7) xc_dom_alloc_page : xenstore : 0xffffffffa25c8000 (pfn 0x225c8) xc_dom_alloc_page : console : 0xffffffffa25c9000 (pfn 0x225c9) nr_page_tables: 0x0000ffffffffffff/48: 0xffff000000000000 -> 0xffffffffffffffff, 1 table(s) nr_page_tables: 0x0000007fffffffff/39: 0xffffff8000000000 -> 0xffffffffffffffff, 1 table(s) nr_page_tables: 0x000000003fffffff/30: 0xffffffff80000000 -> 0xffffffffbfffffff, 1 table(s) nr_page_tables: 0x00000000001fffff/21: 0xffffffff80000000 -> 0xffffffffa27fffff, 276 table(s) xc_dom_alloc_segment: page tables : 0xffffffffa25ca000 -> 0xffffffffa26e1000 (pfn 0x225ca + 0x117 pages) xc_dom_pfn_to_ptr: domU mapping: pfn 0x225ca+0x117 at 0x7f097d7a8000 xc_dom_alloc_page : boot stack : 0xffffffffa26e1000 (pfn 0x226e1) xc_dom_build_image : virt_alloc_end : 0xffffffffa26e2000 xc_dom_build_image : virt_pgtab_end : 0xffffffffa2800000 So the physical memory and virtual (using __START_KERNEL_map addresses) layout looks as so: phys __ka /------------\ /-------------------\ | 0 | empty | 0xffffffff80000000| | .. | | .. | | 16MB | <= kernel starts | 0xffffffff81000000| | .. | | | | 30MB | <= kernel ends => | 0xffffffff81e43000| | .. | & ramdisk starts | .. | | 293MB | <= ramdisk ends=> | 0xffffffff925c7000| | .. | & P2M starts | .. | | .. | | .. | | 549MB | <= P2M ends => | 0xffffffffa25c7000| | .. | start_info | 0xffffffffa25c7000| | .. | xenstore | 0xffffffffa25c8000| | .. | cosole | 0xffffffffa25c9000| | 549MB | <= page tables => | 0xffffffffa25ca000| | .. | | | | 550MB | <= PGT end => | 0xffffffffa26e1000| | .. | boot stack | | \------------/ \-------------------/ As can be seen, the ramdisk, P2M and pagetables are taking a bit of __ka addresses space. Which is a problem since the MODULES_VADDR starts at 0xffffffffa0000000 - and P2M sits right in there! This results during bootup with the inability to load modules, with this error: ------------[ cut here ]------------ WARNING: at /home/konrad/ssd/linux/mm/vmalloc.c:106 vmap_page_range_noflush+0x2d9/0x370() Call Trace: [<ffffffff810719fa>] warn_slowpath_common+0x7a/0xb0 [<ffffffff81030279>] ? __raw_callee_save_xen_pmd_val+0x11/0x1e [<ffffffff81071a45>] warn_slowpath_null+0x15/0x20 [<ffffffff81130b89>] vmap_page_range_noflush+0x2d9/0x370 [<ffffffff81130c4d>] map_vm_area+0x2d/0x50 [<ffffffff811326d0>] __vmalloc_node_range+0x160/0x250 [<ffffffff810c5369>] ? module_alloc_update_bounds+0x19/0x80 [<ffffffff810c6186>] ? load_module+0x66/0x19c0 [<ffffffff8105cadc>] module_alloc+0x5c/0x60 [<ffffffff810c5369>] ? module_alloc_update_bounds+0x19/0x80 [<ffffffff810c5369>] module_alloc_update_bounds+0x19/0x80 [<ffffffff810c70c3>] load_module+0xfa3/0x19c0 [<ffffffff812491f6>] ? security_file_permission+0x86/0x90 [<ffffffff810c7b3a>] sys_init_module+0x5a/0x220 [<ffffffff815ce339>] system_call_fastpath+0x16/0x1b ---[ end trace fd8f7704fdea0291 ]--- vmalloc: allocation failure, allocated 16384 of 20480 bytes modprobe: page allocation failure: order:0, mode:0xd2 Since the __va and __ka are 1:1 up to MODULES_VADDR and cleanup_highmap rids __ka of the ramdisk mapping, what we want to do is similar - get rid of the P2M in the __ka address space. There are two ways of fixing this: 1) All P2M lookups instead of using the __ka address would use the __va address. This means we can safely erase from __ka space the PMD pointers that point to the PFNs for P2M array and be OK. 2). Allocate a new array, copy the existing P2M into it, revector the P2M tree to use that, and return the old P2M to the memory allocate. This has the advantage that it sets the stage for using XEN_ELF_NOTE_INIT_P2M feature. That feature allows us to set the exact virtual address space we want for the P2M - and allows us to boot as initial domain on large machines. So we pick option 2). This patch only lays the groundwork in the P2M code. The patch that modifies the MMU is called "xen/mmu: Copy and revector the P2M tree." Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-07-19 17:52:29 +00:00
if ((unsigned long)mid_p == INVALID_P2M_ENTRY)
continue;
/* The old va. Rebase it on mfn_list */
if (mid_p >= (unsigned long *)va_start && mid_p <= (unsigned long *)va_end) {
unsigned long *new;
new = &mfn_list[pfn];
copy_page(new, mid_p);
p2m_top[topidx][mididx] = &mfn_list[pfn];
p2m_top_mfn_p[topidx][mididx] = virt_to_mfn(&mfn_list[pfn]);
}
/* This should be the leafs allocated for identity from _brk. */
}
return (unsigned long)mfn_list;
}
#else
unsigned long __init xen_revector_p2m_tree(void)
{
return 0;
}
#endif
unsigned long get_phys_to_machine(unsigned long pfn)
{
unsigned topidx, mididx, idx;
if (unlikely(pfn >= MAX_P2M_PFN))
return INVALID_P2M_ENTRY;
topidx = p2m_top_index(pfn);
mididx = p2m_mid_index(pfn);
idx = p2m_index(pfn);
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
/*
* The INVALID_P2M_ENTRY is filled in both p2m_*identity
* and in p2m_*missing, so returning the INVALID_P2M_ENTRY
* would be wrong.
*/
if (p2m_top[topidx][mididx] == p2m_identity)
return IDENTITY_FRAME(pfn);
return p2m_top[topidx][mididx][idx];
}
EXPORT_SYMBOL_GPL(get_phys_to_machine);
static void *alloc_p2m_page(void)
{
return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
}
static void free_p2m_page(void *p)
{
free_page((unsigned long)p);
}
/*
* Fully allocate the p2m structure for a given pfn. We need to check
* that both the top and mid levels are allocated, and make sure the
* parallel mfn tree is kept in sync. We may race with other cpus, so
* the new pages are installed with cmpxchg; if we lose the race then
* simply free the page we allocated and use the one that's there.
*/
static bool alloc_p2m(unsigned long pfn)
{
unsigned topidx, mididx;
unsigned long ***top_p, **mid;
unsigned long *top_mfn_p, *mid_mfn;
topidx = p2m_top_index(pfn);
mididx = p2m_mid_index(pfn);
top_p = &p2m_top[topidx];
mid = *top_p;
if (mid == p2m_mid_missing) {
/* Mid level is missing, allocate a new one */
mid = alloc_p2m_page();
if (!mid)
return false;
p2m_mid_init(mid);
if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing)
free_p2m_page(mid);
}
top_mfn_p = &p2m_top_mfn[topidx];
mid_mfn = p2m_top_mfn_p[topidx];
BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
if (mid_mfn == p2m_mid_missing_mfn) {
/* Separately check the mid mfn level */
unsigned long missing_mfn;
unsigned long mid_mfn_mfn;
mid_mfn = alloc_p2m_page();
if (!mid_mfn)
return false;
p2m_mid_mfn_init(mid_mfn);
missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
mid_mfn_mfn = virt_to_mfn(mid_mfn);
if (cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn) != missing_mfn)
free_p2m_page(mid_mfn);
else
p2m_top_mfn_p[topidx] = mid_mfn;
}
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
if (p2m_top[topidx][mididx] == p2m_identity ||
p2m_top[topidx][mididx] == p2m_missing) {
/* p2m leaf page is missing */
unsigned long *p2m;
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
unsigned long *p2m_orig = p2m_top[topidx][mididx];
p2m = alloc_p2m_page();
if (!p2m)
return false;
p2m_init(p2m);
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
if (cmpxchg(&mid[mididx], p2m_orig, p2m) != p2m_orig)
free_p2m_page(p2m);
else
mid_mfn[mididx] = virt_to_mfn(p2m);
}
return true;
}
static bool __init early_alloc_p2m_middle(unsigned long pfn, bool check_boundary)
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
{
unsigned topidx, mididx, idx;
unsigned long *p2m;
unsigned long *mid_mfn_p;
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
topidx = p2m_top_index(pfn);
mididx = p2m_mid_index(pfn);
idx = p2m_index(pfn);
/* Pfff.. No boundary cross-over, lets get out. */
if (!idx && check_boundary)
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
return false;
WARN(p2m_top[topidx][mididx] == p2m_identity,
"P2M[%d][%d] == IDENTITY, should be MISSING (or alloced)!\n",
topidx, mididx);
/*
* Could be done by xen_build_dynamic_phys_to_machine..
*/
if (p2m_top[topidx][mididx] != p2m_missing)
return false;
/* Boundary cross-over for the edges: */
p2m = extend_brk(PAGE_SIZE, PAGE_SIZE);
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
p2m_init(p2m);
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
p2m_top[topidx][mididx] = p2m;
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
/* For save/restore we need to MFN of the P2M saved */
mid_mfn_p = p2m_top_mfn_p[topidx];
WARN(mid_mfn_p[mididx] != virt_to_mfn(p2m_missing),
"P2M_TOP_P[%d][%d] != MFN of p2m_missing!\n",
topidx, mididx);
mid_mfn_p[mididx] = virt_to_mfn(p2m);
return true;
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
}
static bool __init early_alloc_p2m(unsigned long pfn)
{
unsigned topidx = p2m_top_index(pfn);
unsigned long *mid_mfn_p;
unsigned long **mid;
mid = p2m_top[topidx];
mid_mfn_p = p2m_top_mfn_p[topidx];
if (mid == p2m_mid_missing) {
mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_init(mid);
p2m_top[topidx] = mid;
BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
}
/* And the save/restore P2M tables.. */
if (mid_mfn_p == p2m_mid_missing_mfn) {
mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_mfn_init(mid_mfn_p);
p2m_top_mfn_p[topidx] = mid_mfn_p;
p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
/* Note: we don't set mid_mfn_p[midix] here,
* look in early_alloc_p2m_middle */
}
return true;
}
bool __init early_set_phys_to_machine(unsigned long pfn, unsigned long mfn)
{
if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
if (!early_alloc_p2m(pfn))
return false;
if (!early_alloc_p2m_middle(pfn, false /* boundary crossover OK!*/))
return false;
if (!__set_phys_to_machine(pfn, mfn))
return false;
}
return true;
}
unsigned long __init set_phys_range_identity(unsigned long pfn_s,
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
unsigned long pfn_e)
{
unsigned long pfn;
if (unlikely(pfn_s >= MAX_P2M_PFN || pfn_e >= MAX_P2M_PFN))
return 0;
if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
return pfn_e - pfn_s;
if (pfn_s > pfn_e)
return 0;
for (pfn = (pfn_s & ~(P2M_MID_PER_PAGE * P2M_PER_PAGE - 1));
pfn < ALIGN(pfn_e, (P2M_MID_PER_PAGE * P2M_PER_PAGE));
pfn += P2M_MID_PER_PAGE * P2M_PER_PAGE)
{
WARN_ON(!early_alloc_p2m(pfn));
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
}
early_alloc_p2m_middle(pfn_s, true);
early_alloc_p2m_middle(pfn_e, true);
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
for (pfn = pfn_s; pfn < pfn_e; pfn++)
if (!__set_phys_to_machine(pfn, IDENTITY_FRAME(pfn)))
break;
if (!WARN((pfn - pfn_s) != (pfn_e - pfn_s),
"Identity mapping failed. We are %ld short of 1-1 mappings!\n",
(pfn_e - pfn_s) - (pfn - pfn_s)))
printk(KERN_DEBUG "1-1 mapping on %lx->%lx\n", pfn_s, pfn);
return pfn - pfn_s;
}
/* Try to install p2m mapping; fail if intermediate bits missing */
bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
{
unsigned topidx, mididx, idx;
if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) {
BUG_ON(pfn != mfn && mfn != INVALID_P2M_ENTRY);
return true;
}
if (unlikely(pfn >= MAX_P2M_PFN)) {
BUG_ON(mfn != INVALID_P2M_ENTRY);
return true;
}
topidx = p2m_top_index(pfn);
mididx = p2m_mid_index(pfn);
idx = p2m_index(pfn);
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
/* For sparse holes were the p2m leaf has real PFN along with
* PCI holes, stick in the PFN as the MFN value.
*/
if (mfn != INVALID_P2M_ENTRY && (mfn & IDENTITY_FRAME_BIT)) {
if (p2m_top[topidx][mididx] == p2m_identity)
return true;
/* Swap over from MISSING to IDENTITY if needed. */
if (p2m_top[topidx][mididx] == p2m_missing) {
WARN_ON(cmpxchg(&p2m_top[topidx][mididx], p2m_missing,
p2m_identity) != p2m_missing);
xen/mmu: Add the notion of identity (1-1) mapping. Our P2M tree structure is a three-level. On the leaf nodes we set the Machine Frame Number (MFN) of the PFN. What this means is that when one does: pfn_to_mfn(pfn), which is used when creating PTE entries, you get the real MFN of the hardware. When Xen sets up a guest it initially populates a array which has descending (or ascending) MFN values, as so: idx: 0, 1, 2 [0x290F, 0x290E, 0x290D, ..] so pfn_to_mfn(2)==0x290D. If you start, restart many guests that list starts looking quite random. We graft this structure on our P2M tree structure and stick in those MFN in the leafs. But for all other leaf entries, or for the top root, or middle one, for which there is a void entry, we assume it is "missing". So pfn_to_mfn(0xc0000)=INVALID_P2M_ENTRY. We add the possibility of setting 1-1 mappings on certain regions, so that: pfn_to_mfn(0xc0000)=0xc0000 The benefit of this is, that we can assume for non-RAM regions (think PCI BARs, or ACPI spaces), we can create mappings easily b/c we get the PFN value to match the MFN. For this to work efficiently we introduce one new page p2m_identity and allocate (via reserved_brk) any other pages we need to cover the sides (1GB or 4MB boundary violations). All entries in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, no other fancy value). On lookup we spot that the entry points to p2m_identity and return the identity value instead of dereferencing and returning INVALID_P2M_ENTRY. If the entry points to an allocated page, we just proceed as before and return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in appropriate functions (pfn_to_mfn). The reason for having the IDENTITY_FRAME_BIT instead of just returning the PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a non-identity pfn. To protect ourselves against we elect to set (and get) the IDENTITY_FRAME_BIT on all identity mapped PFNs. This simplistic diagram is used to explain the more subtle piece of code. There is also a digram of the P2M at the end that can help. Imagine your E820 looking as so: 1GB 2GB /-------------------+---------\/----\ /----------\ /---+-----\ | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | \-------------------+---------/\----/ \----------/ \---+-----/ ^- 1029MB ^- 2001MB [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), 2048MB = 524288 (0x80000)] And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB is actually not present (would have to kick the balloon driver to put it in). When we are told to set the PFNs for identity mapping (see patch: "xen/setup: Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start of the PFN and the end PFN (263424 and 512256 respectively). The first step is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page covers 512^2 of page estate (1GB) and in case the start or end PFN is not aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn to end pfn. We reserve_brk top leaf pages if they are missing (means they point to p2m_mid_missing). With the E820 example above, 263424 is not 1GB aligned so we allocate a reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. Each entry in the allocate page is "missing" (points to p2m_missing). Next stage is to determine if we need to do a more granular boundary check on the 4MB (or 2MB depending on architecture) off the start and end pfn's. We check if the start pfn and end pfn violate that boundary check, and if so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer granularity of setting which PFNs are missing and which ones are identity. In our example 263424 and 512256 both fail the check so we reserve_brk two pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" values) and assign them to p2m[1][2] and p2m[1][488] respectively. At this point we would at minimum reserve_brk one page, but could be up to three. Each call to set_phys_range_identity has at maximum a three page cost. If we were to query the P2M at this stage, all those entries from start PFN through end PFN (so 1029MB -> 2001MB) would return INVALID_P2M_ENTRY ("missing"). The next step is to walk from the start pfn to the end pfn setting the IDENTITY_FRAME_BIT on each PFN. This is done in 'set_phys_range_identity'. If we find that the middle leaf is pointing to p2m_missing we can swap it over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this point we do not need to worry about boundary aligment (so no need to reserve_brk a middle page, figure out which PFNs are "missing" and which ones are identity), as that has been done earlier. If we find that the middle leaf is not occupied by p2m_identity or p2m_missing, we dereference that page (which covers 512 PFNs) and set the appropriate PFN with IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we set from p2m[1][2][256->511] and p2m[1][488][0->256] with IDENTITY_FRAME_BIT set. All other regions that are void (or not filled) either point to p2m_missing (considered missing) or have the default value of INVALID_P2M_ENTRY (also considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] contain the INVALID_P2M_ENTRY value and are considered "missing." This is what the p2m ends up looking (for the E820 above) with this fabulous drawing: p2m /--------------\ /-----\ | &mfn_list[0],| /-----------------\ | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | |-----| \ | [p2m_identity]+\\ | .... | | 2 |--\ \-------------------->| ... | \\ \----------------/ |-----| \ \---------------/ \\ | 3 |\ \ \\ p2m_identity |-----| \ \-------------------->/---------------\ /-----------------\ | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | \-----/ / | [p2m_identity]+-->| ..., ~0 | / /---------------\ | .... | \-----------------/ / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | / | IDENTITY[@256]|<----/ \---------------/ / | ~0, ~0, .... | | \---------------/ | p2m_missing p2m_missing /------------------\ /------------\ | [p2m_mid_missing]+---->| ~0, ~0, ~0 | | [p2m_mid_missing]+---->| ..., ~0 | \------------------/ \------------/ where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) Reviewed-by: Ian Campbell <ian.campbell@citrix.com> [v5: Changed code to use ranges, added ASCII art] [v6: Rebased on top of xen->p2m code split] [v4: Squished patches in just this one] [v7: Added RESERVE_BRK for potentially allocated pages] [v8: Fixed alignment problem] [v9: Changed 1<<3X to 1<<BITS_PER_LONG-X] [v10: Copied git commit description in the p2m code + Add Review tag] [v11: Title had '2-1' - should be '1-1' mapping] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-01-19 01:15:21 +00:00
return true;
}
}
if (p2m_top[topidx][mididx] == p2m_missing)
return mfn == INVALID_P2M_ENTRY;
p2m_top[topidx][mididx][idx] = mfn;
return true;
}
bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
{
if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
if (!alloc_p2m(pfn))
return false;
if (!__set_phys_to_machine(pfn, mfn))
return false;
}
return true;
}
#define M2P_OVERRIDE_HASH_SHIFT 10
#define M2P_OVERRIDE_HASH (1 << M2P_OVERRIDE_HASH_SHIFT)
static RESERVE_BRK_ARRAY(struct list_head, m2p_overrides, M2P_OVERRIDE_HASH);
static DEFINE_SPINLOCK(m2p_override_lock);
static void __init m2p_override_init(void)
{
unsigned i;
m2p_overrides = extend_brk(sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH,
sizeof(unsigned long));
for (i = 0; i < M2P_OVERRIDE_HASH; i++)
INIT_LIST_HEAD(&m2p_overrides[i]);
}
static unsigned long mfn_hash(unsigned long mfn)
{
return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT);
}
/* Add an MFN override for a particular page */
int m2p_add_override(unsigned long mfn, struct page *page,
struct gnttab_map_grant_ref *kmap_op)
{
unsigned long flags;
unsigned long pfn;
unsigned long uninitialized_var(address);
unsigned level;
pte_t *ptep = NULL;
xen: mark local pages as FOREIGN in the m2p_override When the frontend and the backend reside on the same domain, even if we add pages to the m2p_override, these pages will never be returned by mfn_to_pfn because the check "get_phys_to_machine(pfn) != mfn" will always fail, so the pfn of the frontend will be returned instead (resulting in a deadlock because the frontend pages are already locked). INFO: task qemu-system-i38:1085 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. qemu-system-i38 D ffff8800cfc137c0 0 1085 1 0x00000000 ffff8800c47ed898 0000000000000282 ffff8800be4596b0 00000000000137c0 ffff8800c47edfd8 ffff8800c47ec010 00000000000137c0 00000000000137c0 ffff8800c47edfd8 00000000000137c0 ffffffff82213020 ffff8800be4596b0 Call Trace: [<ffffffff81101ee0>] ? __lock_page+0x70/0x70 [<ffffffff81a0fdd9>] schedule+0x29/0x70 [<ffffffff81a0fe80>] io_schedule+0x60/0x80 [<ffffffff81101eee>] sleep_on_page+0xe/0x20 [<ffffffff81a0e1ca>] __wait_on_bit_lock+0x5a/0xc0 [<ffffffff81101ed7>] __lock_page+0x67/0x70 [<ffffffff8106f750>] ? autoremove_wake_function+0x40/0x40 [<ffffffff811867e6>] ? bio_add_page+0x36/0x40 [<ffffffff8110b692>] set_page_dirty_lock+0x52/0x60 [<ffffffff81186021>] bio_set_pages_dirty+0x51/0x70 [<ffffffff8118c6b4>] do_blockdev_direct_IO+0xb24/0xeb0 [<ffffffff811e71a0>] ? ext3_get_blocks_handle+0xe00/0xe00 [<ffffffff8118ca95>] __blockdev_direct_IO+0x55/0x60 [<ffffffff811e71a0>] ? ext3_get_blocks_handle+0xe00/0xe00 [<ffffffff811e91c8>] ext3_direct_IO+0xf8/0x390 [<ffffffff811e71a0>] ? ext3_get_blocks_handle+0xe00/0xe00 [<ffffffff81004b60>] ? xen_mc_flush+0xb0/0x1b0 [<ffffffff81104027>] generic_file_aio_read+0x737/0x780 [<ffffffff813bedeb>] ? gnttab_map_refs+0x15b/0x1e0 [<ffffffff811038f0>] ? find_get_pages+0x150/0x150 [<ffffffff8119736c>] aio_rw_vect_retry+0x7c/0x1d0 [<ffffffff811972f0>] ? lookup_ioctx+0x90/0x90 [<ffffffff81198856>] aio_run_iocb+0x66/0x1a0 [<ffffffff811998b8>] do_io_submit+0x708/0xb90 [<ffffffff81199d50>] sys_io_submit+0x10/0x20 [<ffffffff81a18d69>] system_call_fastpath+0x16/0x1b The explanation is in the comment within the code: We need to do this because the pages shared by the frontend (xen-blkfront) can be already locked (lock_page, called by do_read_cache_page); when the userspace backend tries to use them with direct_IO, mfn_to_pfn returns the pfn of the frontend, so do_blockdev_direct_IO is going to try to lock the same pages again resulting in a deadlock. A simplified call graph looks like this: pygrub QEMU ----------------------------------------------- do_read_cache_page io_submit | | lock_page ext3_direct_IO | bio_add_page | lock_page Internally the xen-blkback uses m2p_add_override to swizzle (temporarily) a 'struct page' to have a different MFN (so that it can point to another guest). It also can easily find out whether another pfn corresponding to the mfn exists in the m2p, and can set the FOREIGN bit in the p2m, making sure that mfn_to_pfn returns the pfn of the backend. This allows the backend to perform direct_IO on these pages, but as a side effect prevents the frontend from using get_user_pages_fast on them while they are being shared with the backend. Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-05-23 17:57:20 +00:00
int ret = 0;
pfn = page_to_pfn(page);
if (!PageHighMem(page)) {
address = (unsigned long)__va(pfn << PAGE_SHIFT);
ptep = lookup_address(address, &level);
if (WARN(ptep == NULL || level != PG_LEVEL_4K,
"m2p_add_override: pfn %lx not mapped", pfn))
return -EINVAL;
}
WARN_ON(PagePrivate(page));
SetPagePrivate(page);
set_page_private(page, mfn);
page->index = pfn_to_mfn(pfn);
if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn))))
return -ENOMEM;
if (kmap_op != NULL) {
if (!PageHighMem(page)) {
struct multicall_space mcs =
xen_mc_entry(sizeof(*kmap_op));
MULTI_grant_table_op(mcs.mc,
GNTTABOP_map_grant_ref, kmap_op, 1);
xen_mc_issue(PARAVIRT_LAZY_MMU);
}
/* let's use dev_bus_addr to record the old mfn instead */
kmap_op->dev_bus_addr = page->index;
page->index = (unsigned long) kmap_op;
}
spin_lock_irqsave(&m2p_override_lock, flags);
list_add(&page->lru, &m2p_overrides[mfn_hash(mfn)]);
spin_unlock_irqrestore(&m2p_override_lock, flags);
xen: mark local pages as FOREIGN in the m2p_override When the frontend and the backend reside on the same domain, even if we add pages to the m2p_override, these pages will never be returned by mfn_to_pfn because the check "get_phys_to_machine(pfn) != mfn" will always fail, so the pfn of the frontend will be returned instead (resulting in a deadlock because the frontend pages are already locked). INFO: task qemu-system-i38:1085 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. qemu-system-i38 D ffff8800cfc137c0 0 1085 1 0x00000000 ffff8800c47ed898 0000000000000282 ffff8800be4596b0 00000000000137c0 ffff8800c47edfd8 ffff8800c47ec010 00000000000137c0 00000000000137c0 ffff8800c47edfd8 00000000000137c0 ffffffff82213020 ffff8800be4596b0 Call Trace: [<ffffffff81101ee0>] ? __lock_page+0x70/0x70 [<ffffffff81a0fdd9>] schedule+0x29/0x70 [<ffffffff81a0fe80>] io_schedule+0x60/0x80 [<ffffffff81101eee>] sleep_on_page+0xe/0x20 [<ffffffff81a0e1ca>] __wait_on_bit_lock+0x5a/0xc0 [<ffffffff81101ed7>] __lock_page+0x67/0x70 [<ffffffff8106f750>] ? autoremove_wake_function+0x40/0x40 [<ffffffff811867e6>] ? bio_add_page+0x36/0x40 [<ffffffff8110b692>] set_page_dirty_lock+0x52/0x60 [<ffffffff81186021>] bio_set_pages_dirty+0x51/0x70 [<ffffffff8118c6b4>] do_blockdev_direct_IO+0xb24/0xeb0 [<ffffffff811e71a0>] ? ext3_get_blocks_handle+0xe00/0xe00 [<ffffffff8118ca95>] __blockdev_direct_IO+0x55/0x60 [<ffffffff811e71a0>] ? ext3_get_blocks_handle+0xe00/0xe00 [<ffffffff811e91c8>] ext3_direct_IO+0xf8/0x390 [<ffffffff811e71a0>] ? ext3_get_blocks_handle+0xe00/0xe00 [<ffffffff81004b60>] ? xen_mc_flush+0xb0/0x1b0 [<ffffffff81104027>] generic_file_aio_read+0x737/0x780 [<ffffffff813bedeb>] ? gnttab_map_refs+0x15b/0x1e0 [<ffffffff811038f0>] ? find_get_pages+0x150/0x150 [<ffffffff8119736c>] aio_rw_vect_retry+0x7c/0x1d0 [<ffffffff811972f0>] ? lookup_ioctx+0x90/0x90 [<ffffffff81198856>] aio_run_iocb+0x66/0x1a0 [<ffffffff811998b8>] do_io_submit+0x708/0xb90 [<ffffffff81199d50>] sys_io_submit+0x10/0x20 [<ffffffff81a18d69>] system_call_fastpath+0x16/0x1b The explanation is in the comment within the code: We need to do this because the pages shared by the frontend (xen-blkfront) can be already locked (lock_page, called by do_read_cache_page); when the userspace backend tries to use them with direct_IO, mfn_to_pfn returns the pfn of the frontend, so do_blockdev_direct_IO is going to try to lock the same pages again resulting in a deadlock. A simplified call graph looks like this: pygrub QEMU ----------------------------------------------- do_read_cache_page io_submit | | lock_page ext3_direct_IO | bio_add_page | lock_page Internally the xen-blkback uses m2p_add_override to swizzle (temporarily) a 'struct page' to have a different MFN (so that it can point to another guest). It also can easily find out whether another pfn corresponding to the mfn exists in the m2p, and can set the FOREIGN bit in the p2m, making sure that mfn_to_pfn returns the pfn of the backend. This allows the backend to perform direct_IO on these pages, but as a side effect prevents the frontend from using get_user_pages_fast on them while they are being shared with the backend. Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-05-23 17:57:20 +00:00
/* p2m(m2p(mfn)) == mfn: the mfn is already present somewhere in
* this domain. Set the FOREIGN_FRAME_BIT in the p2m for the other
* pfn so that the following mfn_to_pfn(mfn) calls will return the
* pfn from the m2p_override (the backend pfn) instead.
* We need to do this because the pages shared by the frontend
* (xen-blkfront) can be already locked (lock_page, called by
* do_read_cache_page); when the userspace backend tries to use them
* with direct_IO, mfn_to_pfn returns the pfn of the frontend, so
* do_blockdev_direct_IO is going to try to lock the same pages
* again resulting in a deadlock.
* As a side effect get_user_pages_fast might not be safe on the
* frontend pages while they are being shared with the backend,
* because mfn_to_pfn (that ends up being called by GUPF) will
* return the backend pfn rather than the frontend pfn. */
ret = __get_user(pfn, &machine_to_phys_mapping[mfn]);
if (ret == 0 && get_phys_to_machine(pfn) == mfn)
set_phys_to_machine(pfn, FOREIGN_FRAME(mfn));
return 0;
}
EXPORT_SYMBOL_GPL(m2p_add_override);
xen/p2m/m2p/gnttab: Support GNTMAP_host_map in the M2P override. We only supported the M2P (and P2M) override only for the GNTMAP_contains_pte type mappings. Meaning that we grants operations would "contain the machine address of the PTE to update" If the flag is unset, then the grant operation is "contains a host virtual address". The latter case means that the Hypervisor takes care of updating our page table (specifically the PTE entry) with the guest's MFN. As such we should not try to do anything with the PTE. Previous to this patch we would try to clear the PTE which resulted in Xen hypervisor being upset with us: (XEN) mm.c:1066:d0 Attempt to implicitly unmap a granted PTE c0100000ccc59067 (XEN) domain_crash called from mm.c:1067 (XEN) Domain 0 (vcpu#0) crashed on cpu#3: (XEN) ----[ Xen-4.0-110228 x86_64 debug=y Not tainted ]---- and crashing us. This patch allows us to inhibit the PTE clearing in the PV guest if the GNTMAP_contains_pte is not set. On the m2p_remove_override path we provide the same parameter. Sadly in the grant-table driver we do not have a mechanism to tell m2p_remove_override whether to clear the PTE or not. Since the grant-table driver is used by user-space, we can safely assume that it operates only on PTE's. Hence the implementation for it to work on !GNTMAP_contains_pte returns -EOPNOTSUPP. In the future we can implement the support for this. It will require some extra accounting structure to keep track of the page[i], and the flag. [v1: Added documentation details, made it return -EOPNOTSUPP instead of trying to do a half-way implementation] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2011-02-28 22:58:48 +00:00
int m2p_remove_override(struct page *page, bool clear_pte)
{
unsigned long flags;
unsigned long mfn;
unsigned long pfn;
unsigned long uninitialized_var(address);
unsigned level;
pte_t *ptep = NULL;
xen: mark local pages as FOREIGN in the m2p_override When the frontend and the backend reside on the same domain, even if we add pages to the m2p_override, these pages will never be returned by mfn_to_pfn because the check "get_phys_to_machine(pfn) != mfn" will always fail, so the pfn of the frontend will be returned instead (resulting in a deadlock because the frontend pages are already locked). INFO: task qemu-system-i38:1085 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. qemu-system-i38 D ffff8800cfc137c0 0 1085 1 0x00000000 ffff8800c47ed898 0000000000000282 ffff8800be4596b0 00000000000137c0 ffff8800c47edfd8 ffff8800c47ec010 00000000000137c0 00000000000137c0 ffff8800c47edfd8 00000000000137c0 ffffffff82213020 ffff8800be4596b0 Call Trace: [<ffffffff81101ee0>] ? __lock_page+0x70/0x70 [<ffffffff81a0fdd9>] schedule+0x29/0x70 [<ffffffff81a0fe80>] io_schedule+0x60/0x80 [<ffffffff81101eee>] sleep_on_page+0xe/0x20 [<ffffffff81a0e1ca>] __wait_on_bit_lock+0x5a/0xc0 [<ffffffff81101ed7>] __lock_page+0x67/0x70 [<ffffffff8106f750>] ? autoremove_wake_function+0x40/0x40 [<ffffffff811867e6>] ? bio_add_page+0x36/0x40 [<ffffffff8110b692>] set_page_dirty_lock+0x52/0x60 [<ffffffff81186021>] bio_set_pages_dirty+0x51/0x70 [<ffffffff8118c6b4>] do_blockdev_direct_IO+0xb24/0xeb0 [<ffffffff811e71a0>] ? ext3_get_blocks_handle+0xe00/0xe00 [<ffffffff8118ca95>] __blockdev_direct_IO+0x55/0x60 [<ffffffff811e71a0>] ? ext3_get_blocks_handle+0xe00/0xe00 [<ffffffff811e91c8>] ext3_direct_IO+0xf8/0x390 [<ffffffff811e71a0>] ? ext3_get_blocks_handle+0xe00/0xe00 [<ffffffff81004b60>] ? xen_mc_flush+0xb0/0x1b0 [<ffffffff81104027>] generic_file_aio_read+0x737/0x780 [<ffffffff813bedeb>] ? gnttab_map_refs+0x15b/0x1e0 [<ffffffff811038f0>] ? find_get_pages+0x150/0x150 [<ffffffff8119736c>] aio_rw_vect_retry+0x7c/0x1d0 [<ffffffff811972f0>] ? lookup_ioctx+0x90/0x90 [<ffffffff81198856>] aio_run_iocb+0x66/0x1a0 [<ffffffff811998b8>] do_io_submit+0x708/0xb90 [<ffffffff81199d50>] sys_io_submit+0x10/0x20 [<ffffffff81a18d69>] system_call_fastpath+0x16/0x1b The explanation is in the comment within the code: We need to do this because the pages shared by the frontend (xen-blkfront) can be already locked (lock_page, called by do_read_cache_page); when the userspace backend tries to use them with direct_IO, mfn_to_pfn returns the pfn of the frontend, so do_blockdev_direct_IO is going to try to lock the same pages again resulting in a deadlock. A simplified call graph looks like this: pygrub QEMU ----------------------------------------------- do_read_cache_page io_submit | | lock_page ext3_direct_IO | bio_add_page | lock_page Internally the xen-blkback uses m2p_add_override to swizzle (temporarily) a 'struct page' to have a different MFN (so that it can point to another guest). It also can easily find out whether another pfn corresponding to the mfn exists in the m2p, and can set the FOREIGN bit in the p2m, making sure that mfn_to_pfn returns the pfn of the backend. This allows the backend to perform direct_IO on these pages, but as a side effect prevents the frontend from using get_user_pages_fast on them while they are being shared with the backend. Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-05-23 17:57:20 +00:00
int ret = 0;
pfn = page_to_pfn(page);
mfn = get_phys_to_machine(pfn);
if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT))
return -EINVAL;
if (!PageHighMem(page)) {
address = (unsigned long)__va(pfn << PAGE_SHIFT);
ptep = lookup_address(address, &level);
if (WARN(ptep == NULL || level != PG_LEVEL_4K,
"m2p_remove_override: pfn %lx not mapped", pfn))
return -EINVAL;
}
spin_lock_irqsave(&m2p_override_lock, flags);
list_del(&page->lru);
spin_unlock_irqrestore(&m2p_override_lock, flags);
WARN_ON(!PagePrivate(page));
ClearPagePrivate(page);
if (clear_pte) {
struct gnttab_map_grant_ref *map_op =
(struct gnttab_map_grant_ref *) page->index;
set_phys_to_machine(pfn, map_op->dev_bus_addr);
if (!PageHighMem(page)) {
struct multicall_space mcs;
struct gnttab_unmap_grant_ref *unmap_op;
/*
* It might be that we queued all the m2p grant table
* hypercalls in a multicall, then m2p_remove_override
* get called before the multicall has actually been
* issued. In this case handle is going to -1 because
* it hasn't been modified yet.
*/
if (map_op->handle == -1)
xen_mc_flush();
/*
* Now if map_op->handle is negative it means that the
* hypercall actually returned an error.
*/
if (map_op->handle == GNTST_general_error) {
printk(KERN_WARNING "m2p_remove_override: "
"pfn %lx mfn %lx, failed to modify kernel mappings",
pfn, mfn);
return -1;
}
mcs = xen_mc_entry(
sizeof(struct gnttab_unmap_grant_ref));
unmap_op = mcs.args;
unmap_op->host_addr = map_op->host_addr;
unmap_op->handle = map_op->handle;
unmap_op->dev_bus_addr = 0;
MULTI_grant_table_op(mcs.mc,
GNTTABOP_unmap_grant_ref, unmap_op, 1);
xen_mc_issue(PARAVIRT_LAZY_MMU);
set_pte_at(&init_mm, address, ptep,
pfn_pte(pfn, PAGE_KERNEL));
__flush_tlb_single(address);
map_op->host_addr = 0;
}
} else
set_phys_to_machine(pfn, page->index);
xen: mark local pages as FOREIGN in the m2p_override When the frontend and the backend reside on the same domain, even if we add pages to the m2p_override, these pages will never be returned by mfn_to_pfn because the check "get_phys_to_machine(pfn) != mfn" will always fail, so the pfn of the frontend will be returned instead (resulting in a deadlock because the frontend pages are already locked). INFO: task qemu-system-i38:1085 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. qemu-system-i38 D ffff8800cfc137c0 0 1085 1 0x00000000 ffff8800c47ed898 0000000000000282 ffff8800be4596b0 00000000000137c0 ffff8800c47edfd8 ffff8800c47ec010 00000000000137c0 00000000000137c0 ffff8800c47edfd8 00000000000137c0 ffffffff82213020 ffff8800be4596b0 Call Trace: [<ffffffff81101ee0>] ? __lock_page+0x70/0x70 [<ffffffff81a0fdd9>] schedule+0x29/0x70 [<ffffffff81a0fe80>] io_schedule+0x60/0x80 [<ffffffff81101eee>] sleep_on_page+0xe/0x20 [<ffffffff81a0e1ca>] __wait_on_bit_lock+0x5a/0xc0 [<ffffffff81101ed7>] __lock_page+0x67/0x70 [<ffffffff8106f750>] ? autoremove_wake_function+0x40/0x40 [<ffffffff811867e6>] ? bio_add_page+0x36/0x40 [<ffffffff8110b692>] set_page_dirty_lock+0x52/0x60 [<ffffffff81186021>] bio_set_pages_dirty+0x51/0x70 [<ffffffff8118c6b4>] do_blockdev_direct_IO+0xb24/0xeb0 [<ffffffff811e71a0>] ? ext3_get_blocks_handle+0xe00/0xe00 [<ffffffff8118ca95>] __blockdev_direct_IO+0x55/0x60 [<ffffffff811e71a0>] ? ext3_get_blocks_handle+0xe00/0xe00 [<ffffffff811e91c8>] ext3_direct_IO+0xf8/0x390 [<ffffffff811e71a0>] ? ext3_get_blocks_handle+0xe00/0xe00 [<ffffffff81004b60>] ? xen_mc_flush+0xb0/0x1b0 [<ffffffff81104027>] generic_file_aio_read+0x737/0x780 [<ffffffff813bedeb>] ? gnttab_map_refs+0x15b/0x1e0 [<ffffffff811038f0>] ? find_get_pages+0x150/0x150 [<ffffffff8119736c>] aio_rw_vect_retry+0x7c/0x1d0 [<ffffffff811972f0>] ? lookup_ioctx+0x90/0x90 [<ffffffff81198856>] aio_run_iocb+0x66/0x1a0 [<ffffffff811998b8>] do_io_submit+0x708/0xb90 [<ffffffff81199d50>] sys_io_submit+0x10/0x20 [<ffffffff81a18d69>] system_call_fastpath+0x16/0x1b The explanation is in the comment within the code: We need to do this because the pages shared by the frontend (xen-blkfront) can be already locked (lock_page, called by do_read_cache_page); when the userspace backend tries to use them with direct_IO, mfn_to_pfn returns the pfn of the frontend, so do_blockdev_direct_IO is going to try to lock the same pages again resulting in a deadlock. A simplified call graph looks like this: pygrub QEMU ----------------------------------------------- do_read_cache_page io_submit | | lock_page ext3_direct_IO | bio_add_page | lock_page Internally the xen-blkback uses m2p_add_override to swizzle (temporarily) a 'struct page' to have a different MFN (so that it can point to another guest). It also can easily find out whether another pfn corresponding to the mfn exists in the m2p, and can set the FOREIGN bit in the p2m, making sure that mfn_to_pfn returns the pfn of the backend. This allows the backend to perform direct_IO on these pages, but as a side effect prevents the frontend from using get_user_pages_fast on them while they are being shared with the backend. Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-05-23 17:57:20 +00:00
/* p2m(m2p(mfn)) == FOREIGN_FRAME(mfn): the mfn is already present
* somewhere in this domain, even before being added to the
* m2p_override (see comment above in m2p_add_override).
* If there are no other entries in the m2p_override corresponding
* to this mfn, then remove the FOREIGN_FRAME_BIT from the p2m for
* the original pfn (the one shared by the frontend): the backend
* cannot do any IO on this page anymore because it has been
* unshared. Removing the FOREIGN_FRAME_BIT from the p2m entry of
* the original pfn causes mfn_to_pfn(mfn) to return the frontend
* pfn again. */
mfn &= ~FOREIGN_FRAME_BIT;
ret = __get_user(pfn, &machine_to_phys_mapping[mfn]);
if (ret == 0 && get_phys_to_machine(pfn) == FOREIGN_FRAME(mfn) &&
m2p_find_override(mfn) == NULL)
set_phys_to_machine(pfn, mfn);
return 0;
}
EXPORT_SYMBOL_GPL(m2p_remove_override);
struct page *m2p_find_override(unsigned long mfn)
{
unsigned long flags;
struct list_head *bucket = &m2p_overrides[mfn_hash(mfn)];
struct page *p, *ret;
ret = NULL;
spin_lock_irqsave(&m2p_override_lock, flags);
list_for_each_entry(p, bucket, lru) {
if (page_private(p) == mfn) {
ret = p;
break;
}
}
spin_unlock_irqrestore(&m2p_override_lock, flags);
return ret;
}
unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn)
{
struct page *p = m2p_find_override(mfn);
unsigned long ret = pfn;
if (p)
ret = page_to_pfn(p);
return ret;
}
EXPORT_SYMBOL_GPL(m2p_find_override_pfn);
#ifdef CONFIG_XEN_DEBUG_FS
#include <linux/debugfs.h>
#include "debugfs.h"
static int p2m_dump_show(struct seq_file *m, void *v)
{
static const char * const level_name[] = { "top", "middle",
"entry", "abnormal", "error"};
#define TYPE_IDENTITY 0
#define TYPE_MISSING 1
#define TYPE_PFN 2
#define TYPE_UNKNOWN 3
static const char * const type_name[] = {
[TYPE_IDENTITY] = "identity",
[TYPE_MISSING] = "missing",
[TYPE_PFN] = "pfn",
[TYPE_UNKNOWN] = "abnormal"};
unsigned long pfn, prev_pfn_type = 0, prev_pfn_level = 0;
unsigned int uninitialized_var(prev_level);
unsigned int uninitialized_var(prev_type);
if (!p2m_top)
return 0;
for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn++) {
unsigned topidx = p2m_top_index(pfn);
unsigned mididx = p2m_mid_index(pfn);
unsigned idx = p2m_index(pfn);
unsigned lvl, type;
lvl = 4;
type = TYPE_UNKNOWN;
if (p2m_top[topidx] == p2m_mid_missing) {
lvl = 0; type = TYPE_MISSING;
} else if (p2m_top[topidx] == NULL) {
lvl = 0; type = TYPE_UNKNOWN;
} else if (p2m_top[topidx][mididx] == NULL) {
lvl = 1; type = TYPE_UNKNOWN;
} else if (p2m_top[topidx][mididx] == p2m_identity) {
lvl = 1; type = TYPE_IDENTITY;
} else if (p2m_top[topidx][mididx] == p2m_missing) {
lvl = 1; type = TYPE_MISSING;
} else if (p2m_top[topidx][mididx][idx] == 0) {
lvl = 2; type = TYPE_UNKNOWN;
} else if (p2m_top[topidx][mididx][idx] == IDENTITY_FRAME(pfn)) {
lvl = 2; type = TYPE_IDENTITY;
} else if (p2m_top[topidx][mididx][idx] == INVALID_P2M_ENTRY) {
lvl = 2; type = TYPE_MISSING;
} else if (p2m_top[topidx][mididx][idx] == pfn) {
lvl = 2; type = TYPE_PFN;
} else if (p2m_top[topidx][mididx][idx] != pfn) {
lvl = 2; type = TYPE_PFN;
}
if (pfn == 0) {
prev_level = lvl;
prev_type = type;
}
if (pfn == MAX_DOMAIN_PAGES-1) {
lvl = 3;
type = TYPE_UNKNOWN;
}
if (prev_type != type) {
seq_printf(m, " [0x%lx->0x%lx] %s\n",
prev_pfn_type, pfn, type_name[prev_type]);
prev_pfn_type = pfn;
prev_type = type;
}
if (prev_level != lvl) {
seq_printf(m, " [0x%lx->0x%lx] level %s\n",
prev_pfn_level, pfn, level_name[prev_level]);
prev_pfn_level = pfn;
prev_level = lvl;
}
}
return 0;
#undef TYPE_IDENTITY
#undef TYPE_MISSING
#undef TYPE_PFN
#undef TYPE_UNKNOWN
}
static int p2m_dump_open(struct inode *inode, struct file *filp)
{
return single_open(filp, p2m_dump_show, NULL);
}
static const struct file_operations p2m_dump_fops = {
.open = p2m_dump_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
static struct dentry *d_mmu_debug;
static int __init xen_p2m_debugfs(void)
{
struct dentry *d_xen = xen_init_debugfs();
if (d_xen == NULL)
return -ENOMEM;
d_mmu_debug = debugfs_create_dir("mmu", d_xen);
debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops);
return 0;
}
fs_initcall(xen_p2m_debugfs);
#endif /* CONFIG_XEN_DEBUG_FS */