linux/arch/powerpc/mm/hugetlbpage.c
Benjamin Herrenschmidt d0f13e3c20 [POWERPC] Introduce address space "slices"
The basic issue is to be able to do what hugetlbfs does but with
different page sizes for some other special filesystems; more
specifically, my need is:

 - Huge pages

 - SPE local store mappings using 64K pages on a 4K base page size
kernel on Cell

 - Some special 4K segments in 64K-page kernels for mapping a dodgy
type of powerpc-specific infiniband hardware that requires 4K MMU
mappings for various reasons I won't explain here.

The main issues are:

 - To maintain/keep track of the page size per "segment" (as we can
only have one page size per segment on powerpc, which are 256MB
divisions of the address space).

 - To make sure special mappings stay within their allotted
"segments" (including MAP_FIXED crap)

 - To make sure everybody else doesn't mmap/brk/grow_stack into a
"segment" that is used for a special mapping

Some of the necessary mechanisms to handle that were present in the
hugetlbfs code, but mostly in ways not suitable for anything else.

The patch relies on some changes to the generic get_unmapped_area()
that just got merged.  It still hijacks hugetlb callbacks here or
there as the generic code hasn't been entirely cleaned up yet but
that shouldn't be a problem.

So what is a slice ?  Well, I re-used the mechanism used formerly by our
hugetlbfs implementation which divides the address space in
"meta-segments" which I called "slices".  The division is done using
256MB slices below 4G, and 1T slices above.  Thus the address space is
divided currently into 16 "low" slices and 16 "high" slices.  (Special
case: high slice 0 is the area between 4G and 1T).

Doing so simplifies significantly the tracking of segments and avoids
having to keep track of all the 256MB segments in the address space.

While I used the "concepts" of hugetlbfs, I mostly re-implemented
everything in a more generic way and "ported" hugetlbfs to it.

Slices can have an associated page size, which is encoded in the mmu
context and used by the SLB miss handler to set the segment sizes.  The
hash code currently doesn't care, it has a specific check for hugepages,
though I might add a mechanism to provide per-slice hash mapping
functions in the future.

The slice code provide a pair of "generic" get_unmapped_area() (bottomup
and topdown) functions that should work with any slice size.  There is
some trickiness here so I would appreciate people to have a look at the
implementation of these and let me know if I got something wrong.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
2007-05-09 16:35:00 +10:00

553 lines
13 KiB
C

/*
* PPC64 (POWER4) Huge TLB Page Support for Kernel.
*
* Copyright (C) 2003 David Gibson, IBM Corporation.
*
* Based on the IA-32 version:
* Copyright (C) 2002, Rohit Seth <rohit.seth@intel.com>
*/
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/sysctl.h>
#include <asm/mman.h>
#include <asm/pgalloc.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
#include <asm/machdep.h>
#include <asm/cputable.h>
#include <asm/tlb.h>
#include <asm/spu.h>
#include <linux/sysctl.h>
#define NUM_LOW_AREAS (0x100000000UL >> SID_SHIFT)
#define NUM_HIGH_AREAS (PGTABLE_RANGE >> HTLB_AREA_SHIFT)
#ifdef CONFIG_PPC_64K_PAGES
#define HUGEPTE_INDEX_SIZE (PMD_SHIFT-HPAGE_SHIFT)
#else
#define HUGEPTE_INDEX_SIZE (PUD_SHIFT-HPAGE_SHIFT)
#endif
#define PTRS_PER_HUGEPTE (1 << HUGEPTE_INDEX_SIZE)
#define HUGEPTE_TABLE_SIZE (sizeof(pte_t) << HUGEPTE_INDEX_SIZE)
#define HUGEPD_SHIFT (HPAGE_SHIFT + HUGEPTE_INDEX_SIZE)
#define HUGEPD_SIZE (1UL << HUGEPD_SHIFT)
#define HUGEPD_MASK (~(HUGEPD_SIZE-1))
#define huge_pgtable_cache (pgtable_cache[HUGEPTE_CACHE_NUM])
/* Flag to mark huge PD pointers. This means pmd_bad() and pud_bad()
* will choke on pointers to hugepte tables, which is handy for
* catching screwups early. */
#define HUGEPD_OK 0x1
typedef struct { unsigned long pd; } hugepd_t;
#define hugepd_none(hpd) ((hpd).pd == 0)
static inline pte_t *hugepd_page(hugepd_t hpd)
{
BUG_ON(!(hpd.pd & HUGEPD_OK));
return (pte_t *)(hpd.pd & ~HUGEPD_OK);
}
static inline pte_t *hugepte_offset(hugepd_t *hpdp, unsigned long addr)
{
unsigned long idx = ((addr >> HPAGE_SHIFT) & (PTRS_PER_HUGEPTE-1));
pte_t *dir = hugepd_page(*hpdp);
return dir + idx;
}
static int __hugepte_alloc(struct mm_struct *mm, hugepd_t *hpdp,
unsigned long address)
{
pte_t *new = kmem_cache_alloc(huge_pgtable_cache,
GFP_KERNEL|__GFP_REPEAT);
if (! new)
return -ENOMEM;
spin_lock(&mm->page_table_lock);
if (!hugepd_none(*hpdp))
kmem_cache_free(huge_pgtable_cache, new);
else
hpdp->pd = (unsigned long)new | HUGEPD_OK;
spin_unlock(&mm->page_table_lock);
return 0;
}
/* Modelled after find_linux_pte() */
pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
{
pgd_t *pg;
pud_t *pu;
BUG_ON(get_slice_psize(mm, addr) != mmu_huge_psize);
addr &= HPAGE_MASK;
pg = pgd_offset(mm, addr);
if (!pgd_none(*pg)) {
pu = pud_offset(pg, addr);
if (!pud_none(*pu)) {
#ifdef CONFIG_PPC_64K_PAGES
pmd_t *pm;
pm = pmd_offset(pu, addr);
if (!pmd_none(*pm))
return hugepte_offset((hugepd_t *)pm, addr);
#else
return hugepte_offset((hugepd_t *)pu, addr);
#endif
}
}
return NULL;
}
pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr)
{
pgd_t *pg;
pud_t *pu;
hugepd_t *hpdp = NULL;
BUG_ON(get_slice_psize(mm, addr) != mmu_huge_psize);
addr &= HPAGE_MASK;
pg = pgd_offset(mm, addr);
pu = pud_alloc(mm, pg, addr);
if (pu) {
#ifdef CONFIG_PPC_64K_PAGES
pmd_t *pm;
pm = pmd_alloc(mm, pu, addr);
if (pm)
hpdp = (hugepd_t *)pm;
#else
hpdp = (hugepd_t *)pu;
#endif
}
if (! hpdp)
return NULL;
if (hugepd_none(*hpdp) && __hugepte_alloc(mm, hpdp, addr))
return NULL;
return hugepte_offset(hpdp, addr);
}
int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
{
return 0;
}
static void free_hugepte_range(struct mmu_gather *tlb, hugepd_t *hpdp)
{
pte_t *hugepte = hugepd_page(*hpdp);
hpdp->pd = 0;
tlb->need_flush = 1;
pgtable_free_tlb(tlb, pgtable_free_cache(hugepte, HUGEPTE_CACHE_NUM,
PGF_CACHENUM_MASK));
}
#ifdef CONFIG_PPC_64K_PAGES
static void hugetlb_free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
unsigned long addr, unsigned long end,
unsigned long floor, unsigned long ceiling)
{
pmd_t *pmd;
unsigned long next;
unsigned long start;
start = addr;
pmd = pmd_offset(pud, addr);
do {
next = pmd_addr_end(addr, end);
if (pmd_none(*pmd))
continue;
free_hugepte_range(tlb, (hugepd_t *)pmd);
} while (pmd++, addr = next, addr != end);
start &= PUD_MASK;
if (start < floor)
return;
if (ceiling) {
ceiling &= PUD_MASK;
if (!ceiling)
return;
}
if (end - 1 > ceiling - 1)
return;
pmd = pmd_offset(pud, start);
pud_clear(pud);
pmd_free_tlb(tlb, pmd);
}
#endif
static void hugetlb_free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
unsigned long addr, unsigned long end,
unsigned long floor, unsigned long ceiling)
{
pud_t *pud;
unsigned long next;
unsigned long start;
start = addr;
pud = pud_offset(pgd, addr);
do {
next = pud_addr_end(addr, end);
#ifdef CONFIG_PPC_64K_PAGES
if (pud_none_or_clear_bad(pud))
continue;
hugetlb_free_pmd_range(tlb, pud, addr, next, floor, ceiling);
#else
if (pud_none(*pud))
continue;
free_hugepte_range(tlb, (hugepd_t *)pud);
#endif
} while (pud++, addr = next, addr != end);
start &= PGDIR_MASK;
if (start < floor)
return;
if (ceiling) {
ceiling &= PGDIR_MASK;
if (!ceiling)
return;
}
if (end - 1 > ceiling - 1)
return;
pud = pud_offset(pgd, start);
pgd_clear(pgd);
pud_free_tlb(tlb, pud);
}
/*
* This function frees user-level page tables of a process.
*
* Must be called with pagetable lock held.
*/
void hugetlb_free_pgd_range(struct mmu_gather **tlb,
unsigned long addr, unsigned long end,
unsigned long floor, unsigned long ceiling)
{
pgd_t *pgd;
unsigned long next;
unsigned long start;
/*
* Comments below take from the normal free_pgd_range(). They
* apply here too. The tests against HUGEPD_MASK below are
* essential, because we *don't* test for this at the bottom
* level. Without them we'll attempt to free a hugepte table
* when we unmap just part of it, even if there are other
* active mappings using it.
*
* The next few lines have given us lots of grief...
*
* Why are we testing HUGEPD* at this top level? Because
* often there will be no work to do at all, and we'd prefer
* not to go all the way down to the bottom just to discover
* that.
*
* Why all these "- 1"s? Because 0 represents both the bottom
* of the address space and the top of it (using -1 for the
* top wouldn't help much: the masks would do the wrong thing).
* The rule is that addr 0 and floor 0 refer to the bottom of
* the address space, but end 0 and ceiling 0 refer to the top
* Comparisons need to use "end - 1" and "ceiling - 1" (though
* that end 0 case should be mythical).
*
* Wherever addr is brought up or ceiling brought down, we
* must be careful to reject "the opposite 0" before it
* confuses the subsequent tests. But what about where end is
* brought down by HUGEPD_SIZE below? no, end can't go down to
* 0 there.
*
* Whereas we round start (addr) and ceiling down, by different
* masks at different levels, in order to test whether a table
* now has no other vmas using it, so can be freed, we don't
* bother to round floor or end up - the tests don't need that.
*/
addr &= HUGEPD_MASK;
if (addr < floor) {
addr += HUGEPD_SIZE;
if (!addr)
return;
}
if (ceiling) {
ceiling &= HUGEPD_MASK;
if (!ceiling)
return;
}
if (end - 1 > ceiling - 1)
end -= HUGEPD_SIZE;
if (addr > end - 1)
return;
start = addr;
pgd = pgd_offset((*tlb)->mm, addr);
do {
BUG_ON(get_slice_psize((*tlb)->mm, addr) != mmu_huge_psize);
next = pgd_addr_end(addr, end);
if (pgd_none_or_clear_bad(pgd))
continue;
hugetlb_free_pud_range(*tlb, pgd, addr, next, floor, ceiling);
} while (pgd++, addr = next, addr != end);
}
void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
pte_t *ptep, pte_t pte)
{
if (pte_present(*ptep)) {
/* We open-code pte_clear because we need to pass the right
* argument to hpte_need_flush (huge / !huge). Might not be
* necessary anymore if we make hpte_need_flush() get the
* page size from the slices
*/
pte_update(mm, addr & HPAGE_MASK, ptep, ~0UL, 1);
}
*ptep = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS);
}
pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
pte_t *ptep)
{
unsigned long old = pte_update(mm, addr, ptep, ~0UL, 1);
return __pte(old);
}
struct page *
follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
{
pte_t *ptep;
struct page *page;
if (get_slice_psize(mm, address) != mmu_huge_psize)
return ERR_PTR(-EINVAL);
ptep = huge_pte_offset(mm, address);
page = pte_page(*ptep);
if (page)
page += (address % HPAGE_SIZE) / PAGE_SIZE;
return page;
}
int pmd_huge(pmd_t pmd)
{
return 0;
}
struct page *
follow_huge_pmd(struct mm_struct *mm, unsigned long address,
pmd_t *pmd, int write)
{
BUG();
return NULL;
}
unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
unsigned long len, unsigned long pgoff,
unsigned long flags)
{
return slice_get_unmapped_area(addr, len, flags,
mmu_huge_psize, 1, 0);
}
/*
* Called by asm hashtable.S for doing lazy icache flush
*/
static unsigned int hash_huge_page_do_lazy_icache(unsigned long rflags,
pte_t pte, int trap)
{
struct page *page;
int i;
if (!pfn_valid(pte_pfn(pte)))
return rflags;
page = pte_page(pte);
/* page is dirty */
if (!test_bit(PG_arch_1, &page->flags) && !PageReserved(page)) {
if (trap == 0x400) {
for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++)
__flush_dcache_icache(page_address(page+i));
set_bit(PG_arch_1, &page->flags);
} else {
rflags |= HPTE_R_N;
}
}
return rflags;
}
int hash_huge_page(struct mm_struct *mm, unsigned long access,
unsigned long ea, unsigned long vsid, int local,
unsigned long trap)
{
pte_t *ptep;
unsigned long old_pte, new_pte;
unsigned long va, rflags, pa;
long slot;
int err = 1;
ptep = huge_pte_offset(mm, ea);
/* Search the Linux page table for a match with va */
va = (vsid << 28) | (ea & 0x0fffffff);
/*
* If no pte found or not present, send the problem up to
* do_page_fault
*/
if (unlikely(!ptep || pte_none(*ptep)))
goto out;
/*
* Check the user's access rights to the page. If access should be
* prevented then send the problem up to do_page_fault.
*/
if (unlikely(access & ~pte_val(*ptep)))
goto out;
/*
* At this point, we have a pte (old_pte) which can be used to build
* or update an HPTE. There are 2 cases:
*
* 1. There is a valid (present) pte with no associated HPTE (this is
* the most common case)
* 2. There is a valid (present) pte with an associated HPTE. The
* current values of the pp bits in the HPTE prevent access
* because we are doing software DIRTY bit management and the
* page is currently not DIRTY.
*/
do {
old_pte = pte_val(*ptep);
if (old_pte & _PAGE_BUSY)
goto out;
new_pte = old_pte | _PAGE_BUSY |
_PAGE_ACCESSED | _PAGE_HASHPTE;
} while(old_pte != __cmpxchg_u64((unsigned long *)ptep,
old_pte, new_pte));
rflags = 0x2 | (!(new_pte & _PAGE_RW));
/* _PAGE_EXEC -> HW_NO_EXEC since it's inverted */
rflags |= ((new_pte & _PAGE_EXEC) ? 0 : HPTE_R_N);
if (!cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
/* No CPU has hugepages but lacks no execute, so we
* don't need to worry about that case */
rflags = hash_huge_page_do_lazy_icache(rflags, __pte(old_pte),
trap);
/* Check if pte already has an hpte (case 2) */
if (unlikely(old_pte & _PAGE_HASHPTE)) {
/* There MIGHT be an HPTE for this pte */
unsigned long hash, slot;
hash = hpt_hash(va, HPAGE_SHIFT);
if (old_pte & _PAGE_F_SECOND)
hash = ~hash;
slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
slot += (old_pte & _PAGE_F_GIX) >> 12;
if (ppc_md.hpte_updatepp(slot, rflags, va, mmu_huge_psize,
local) == -1)
old_pte &= ~_PAGE_HPTEFLAGS;
}
if (likely(!(old_pte & _PAGE_HASHPTE))) {
unsigned long hash = hpt_hash(va, HPAGE_SHIFT);
unsigned long hpte_group;
pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;
repeat:
hpte_group = ((hash & htab_hash_mask) *
HPTES_PER_GROUP) & ~0x7UL;
/* clear HPTE slot informations in new PTE */
new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | _PAGE_HASHPTE;
/* Add in WIMG bits */
/* XXX We should store these in the pte */
/* --BenH: I think they are ... */
rflags |= _PAGE_COHERENT;
/* Insert into the hash table, primary slot */
slot = ppc_md.hpte_insert(hpte_group, va, pa, rflags, 0,
mmu_huge_psize);
/* Primary is full, try the secondary */
if (unlikely(slot == -1)) {
hpte_group = ((~hash & htab_hash_mask) *
HPTES_PER_GROUP) & ~0x7UL;
slot = ppc_md.hpte_insert(hpte_group, va, pa, rflags,
HPTE_V_SECONDARY,
mmu_huge_psize);
if (slot == -1) {
if (mftb() & 0x1)
hpte_group = ((hash & htab_hash_mask) *
HPTES_PER_GROUP)&~0x7UL;
ppc_md.hpte_remove(hpte_group);
goto repeat;
}
}
if (unlikely(slot == -2))
panic("hash_huge_page: pte_insert failed\n");
new_pte |= (slot << 12) & (_PAGE_F_SECOND | _PAGE_F_GIX);
}
/*
* No need to use ldarx/stdcx here
*/
*ptep = __pte(new_pte & ~_PAGE_BUSY);
err = 0;
out:
return err;
}
static void zero_ctor(void *addr, struct kmem_cache *cache, unsigned long flags)
{
memset(addr, 0, kmem_cache_size(cache));
}
static int __init hugetlbpage_init(void)
{
if (!cpu_has_feature(CPU_FTR_16M_PAGE))
return -ENODEV;
huge_pgtable_cache = kmem_cache_create("hugepte_cache",
HUGEPTE_TABLE_SIZE,
HUGEPTE_TABLE_SIZE,
0,
zero_ctor, NULL);
if (! huge_pgtable_cache)
panic("hugetlbpage_init(): could not create hugepte cache\n");
return 0;
}
module_init(hugetlbpage_init);