linux/drivers/xen/balloon.c
Boris Ostrovsky b3cf8528bb xen/balloon: Mark unallocated host memory as UNUSABLE
Commit f5775e0b61 ("x86/xen: discard RAM regions above the maximum
reservation") left host memory not assigned to dom0 as available for
memory hotplug.

Unfortunately this also meant that those regions could be used by
others. Specifically, commit fa564ad963 ("x86/PCI: Enable a 64bit BAR
on AMD Family 15h (Models 00-1f, 30-3f, 60-7f)") may try to map those
addresses as MMIO.

To prevent this mark unallocated host memory as E820_TYPE_UNUSABLE (thus
effectively reverting f5775e0b61) and keep track of that region as
a hostmem resource that can be used for the hotplug.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
2017-12-20 13:16:20 -05:00

838 lines
20 KiB
C

/******************************************************************************
* Xen balloon driver - enables returning/claiming memory to/from Xen.
*
* Copyright (c) 2003, B Dragovic
* Copyright (c) 2003-2004, M Williamson, K Fraser
* Copyright (c) 2005 Dan M. Smith, IBM Corporation
* Copyright (c) 2010 Daniel Kiper
*
* Memory hotplug support was written by Daniel Kiper. Work on
* it was sponsored by Google under Google Summer of Code 2010
* program. Jeremy Fitzhardinge from Citrix was the mentor for
* this project.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation; or, when distributed
* separately from the Linux kernel or incorporated into other
* software packages, subject to the following license:
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this source file (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy, modify,
* merge, publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
#include <linux/cpu.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/cred.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/bootmem.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/mutex.h>
#include <linux/list.h>
#include <linux/gfp.h>
#include <linux/notifier.h>
#include <linux/memory.h>
#include <linux/memory_hotplug.h>
#include <linux/percpu-defs.h>
#include <linux/slab.h>
#include <linux/sysctl.h>
#include <asm/page.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/tlb.h>
#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>
#include <xen/xen.h>
#include <xen/interface/xen.h>
#include <xen/interface/memory.h>
#include <xen/balloon.h>
#include <xen/features.h>
#include <xen/page.h>
static int xen_hotplug_unpopulated;
#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
static int zero;
static int one = 1;
static struct ctl_table balloon_table[] = {
{
.procname = "hotplug_unpopulated",
.data = &xen_hotplug_unpopulated,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = &zero,
.extra2 = &one,
},
{ }
};
static struct ctl_table balloon_root[] = {
{
.procname = "balloon",
.mode = 0555,
.child = balloon_table,
},
{ }
};
static struct ctl_table xen_root[] = {
{
.procname = "xen",
.mode = 0555,
.child = balloon_root,
},
{ }
};
#endif
/*
* Use one extent per PAGE_SIZE to avoid to break down the page into
* multiple frame.
*/
#define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
/*
* balloon_process() state:
*
* BP_DONE: done or nothing to do,
* BP_WAIT: wait to be rescheduled,
* BP_EAGAIN: error, go to sleep,
* BP_ECANCELED: error, balloon operation canceled.
*/
enum bp_state {
BP_DONE,
BP_WAIT,
BP_EAGAIN,
BP_ECANCELED
};
static DEFINE_MUTEX(balloon_mutex);
struct balloon_stats balloon_stats;
EXPORT_SYMBOL_GPL(balloon_stats);
/* We increase/decrease in batches which fit in a page */
static xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)];
/* List of ballooned pages, threaded through the mem_map array. */
static LIST_HEAD(ballooned_pages);
static DECLARE_WAIT_QUEUE_HEAD(balloon_wq);
/* Main work function, always executed in process context. */
static void balloon_process(struct work_struct *work);
static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);
/* When ballooning out (allocating memory to return to Xen) we don't really
want the kernel to try too hard since that can trigger the oom killer. */
#define GFP_BALLOON \
(GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
static void scrub_page(struct page *page)
{
#ifdef CONFIG_XEN_SCRUB_PAGES
clear_highpage(page);
#endif
}
/* balloon_append: add the given page to the balloon. */
static void __balloon_append(struct page *page)
{
/* Lowmem is re-populated first, so highmem pages go at list tail. */
if (PageHighMem(page)) {
list_add_tail(&page->lru, &ballooned_pages);
balloon_stats.balloon_high++;
} else {
list_add(&page->lru, &ballooned_pages);
balloon_stats.balloon_low++;
}
wake_up(&balloon_wq);
}
static void balloon_append(struct page *page)
{
__balloon_append(page);
}
/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
static struct page *balloon_retrieve(bool require_lowmem)
{
struct page *page;
if (list_empty(&ballooned_pages))
return NULL;
page = list_entry(ballooned_pages.next, struct page, lru);
if (require_lowmem && PageHighMem(page))
return NULL;
list_del(&page->lru);
if (PageHighMem(page))
balloon_stats.balloon_high--;
else
balloon_stats.balloon_low--;
return page;
}
static struct page *balloon_next_page(struct page *page)
{
struct list_head *next = page->lru.next;
if (next == &ballooned_pages)
return NULL;
return list_entry(next, struct page, lru);
}
static enum bp_state update_schedule(enum bp_state state)
{
if (state == BP_WAIT)
return BP_WAIT;
if (state == BP_ECANCELED)
return BP_ECANCELED;
if (state == BP_DONE) {
balloon_stats.schedule_delay = 1;
balloon_stats.retry_count = 1;
return BP_DONE;
}
++balloon_stats.retry_count;
if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
balloon_stats.retry_count > balloon_stats.max_retry_count) {
balloon_stats.schedule_delay = 1;
balloon_stats.retry_count = 1;
return BP_ECANCELED;
}
balloon_stats.schedule_delay <<= 1;
if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
return BP_EAGAIN;
}
#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
static void release_memory_resource(struct resource *resource)
{
if (!resource)
return;
/*
* No need to reset region to identity mapped since we now
* know that no I/O can be in this region
*/
release_resource(resource);
kfree(resource);
}
/*
* Host memory not allocated to dom0. We can use this range for hotplug-based
* ballooning.
*
* It's a type-less resource. Setting IORESOURCE_MEM will make resource
* management algorithms (arch_remove_reservations()) look into guest e820,
* which we don't want.
*/
static struct resource hostmem_resource = {
.name = "Host RAM",
};
void __attribute__((weak)) __init arch_xen_balloon_init(struct resource *res)
{}
static struct resource *additional_memory_resource(phys_addr_t size)
{
struct resource *res, *res_hostmem;
int ret = -ENOMEM;
res = kzalloc(sizeof(*res), GFP_KERNEL);
if (!res)
return NULL;
res->name = "System RAM";
res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
res_hostmem = kzalloc(sizeof(*res), GFP_KERNEL);
if (res_hostmem) {
/* Try to grab a range from hostmem */
res_hostmem->name = "Host memory";
ret = allocate_resource(&hostmem_resource, res_hostmem,
size, 0, -1,
PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
}
if (!ret) {
/*
* Insert this resource into iomem. Because hostmem_resource
* tracks portion of guest e820 marked as UNUSABLE noone else
* should try to use it.
*/
res->start = res_hostmem->start;
res->end = res_hostmem->end;
ret = insert_resource(&iomem_resource, res);
if (ret < 0) {
pr_err("Can't insert iomem_resource [%llx - %llx]\n",
res->start, res->end);
release_memory_resource(res_hostmem);
res_hostmem = NULL;
res->start = res->end = 0;
}
}
if (ret) {
ret = allocate_resource(&iomem_resource, res,
size, 0, -1,
PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
if (ret < 0) {
pr_err("Cannot allocate new System RAM resource\n");
kfree(res);
return NULL;
}
}
#ifdef CONFIG_SPARSEMEM
{
unsigned long limit = 1UL << (MAX_PHYSMEM_BITS - PAGE_SHIFT);
unsigned long pfn = res->start >> PAGE_SHIFT;
if (pfn > limit) {
pr_err("New System RAM resource outside addressable RAM (%lu > %lu)\n",
pfn, limit);
release_memory_resource(res);
release_memory_resource(res_hostmem);
return NULL;
}
}
#endif
return res;
}
static enum bp_state reserve_additional_memory(void)
{
long credit;
struct resource *resource;
int nid, rc;
unsigned long balloon_hotplug;
credit = balloon_stats.target_pages + balloon_stats.target_unpopulated
- balloon_stats.total_pages;
/*
* Already hotplugged enough pages? Wait for them to be
* onlined.
*/
if (credit <= 0)
return BP_WAIT;
balloon_hotplug = round_up(credit, PAGES_PER_SECTION);
resource = additional_memory_resource(balloon_hotplug * PAGE_SIZE);
if (!resource)
goto err;
nid = memory_add_physaddr_to_nid(resource->start);
#ifdef CONFIG_XEN_HAVE_PVMMU
/*
* We don't support PV MMU when Linux and Xen is using
* different page granularity.
*/
BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
/*
* add_memory() will build page tables for the new memory so
* the p2m must contain invalid entries so the correct
* non-present PTEs will be written.
*
* If a failure occurs, the original (identity) p2m entries
* are not restored since this region is now known not to
* conflict with any devices.
*/
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
unsigned long pfn, i;
pfn = PFN_DOWN(resource->start);
for (i = 0; i < balloon_hotplug; i++) {
if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
pr_warn("set_phys_to_machine() failed, no memory added\n");
goto err;
}
}
}
#endif
/*
* add_memory_resource() will call online_pages() which in its turn
* will call xen_online_page() callback causing deadlock if we don't
* release balloon_mutex here. Unlocking here is safe because the
* callers drop the mutex before trying again.
*/
mutex_unlock(&balloon_mutex);
rc = add_memory_resource(nid, resource, memhp_auto_online);
mutex_lock(&balloon_mutex);
if (rc) {
pr_warn("Cannot add additional memory (%i)\n", rc);
goto err;
}
balloon_stats.total_pages += balloon_hotplug;
return BP_WAIT;
err:
release_memory_resource(resource);
return BP_ECANCELED;
}
static void xen_online_page(struct page *page)
{
__online_page_set_limits(page);
mutex_lock(&balloon_mutex);
__balloon_append(page);
mutex_unlock(&balloon_mutex);
}
static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
{
if (val == MEM_ONLINE)
schedule_delayed_work(&balloon_worker, 0);
return NOTIFY_OK;
}
static struct notifier_block xen_memory_nb = {
.notifier_call = xen_memory_notifier,
.priority = 0
};
#else
static enum bp_state reserve_additional_memory(void)
{
balloon_stats.target_pages = balloon_stats.current_pages;
return BP_ECANCELED;
}
#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
static long current_credit(void)
{
return balloon_stats.target_pages - balloon_stats.current_pages;
}
static bool balloon_is_inflated(void)
{
return balloon_stats.balloon_low || balloon_stats.balloon_high;
}
static enum bp_state increase_reservation(unsigned long nr_pages)
{
int rc;
unsigned long i;
struct page *page;
struct xen_memory_reservation reservation = {
.address_bits = 0,
.extent_order = EXTENT_ORDER,
.domid = DOMID_SELF
};
if (nr_pages > ARRAY_SIZE(frame_list))
nr_pages = ARRAY_SIZE(frame_list);
page = list_first_entry_or_null(&ballooned_pages, struct page, lru);
for (i = 0; i < nr_pages; i++) {
if (!page) {
nr_pages = i;
break;
}
/* XENMEM_populate_physmap requires a PFN based on Xen
* granularity.
*/
frame_list[i] = page_to_xen_pfn(page);
page = balloon_next_page(page);
}
set_xen_guest_handle(reservation.extent_start, frame_list);
reservation.nr_extents = nr_pages;
rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
if (rc <= 0)
return BP_EAGAIN;
for (i = 0; i < rc; i++) {
page = balloon_retrieve(false);
BUG_ON(page == NULL);
#ifdef CONFIG_XEN_HAVE_PVMMU
/*
* We don't support PV MMU when Linux and Xen is using
* different page granularity.
*/
BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
unsigned long pfn = page_to_pfn(page);
set_phys_to_machine(pfn, frame_list[i]);
/* Link back into the page tables if not highmem. */
if (!PageHighMem(page)) {
int ret;
ret = HYPERVISOR_update_va_mapping(
(unsigned long)__va(pfn << PAGE_SHIFT),
mfn_pte(frame_list[i], PAGE_KERNEL),
0);
BUG_ON(ret);
}
}
#endif
/* Relinquish the page back to the allocator. */
free_reserved_page(page);
}
balloon_stats.current_pages += rc;
return BP_DONE;
}
static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
{
enum bp_state state = BP_DONE;
unsigned long i;
struct page *page, *tmp;
int ret;
struct xen_memory_reservation reservation = {
.address_bits = 0,
.extent_order = EXTENT_ORDER,
.domid = DOMID_SELF
};
LIST_HEAD(pages);
if (nr_pages > ARRAY_SIZE(frame_list))
nr_pages = ARRAY_SIZE(frame_list);
for (i = 0; i < nr_pages; i++) {
page = alloc_page(gfp);
if (page == NULL) {
nr_pages = i;
state = BP_EAGAIN;
break;
}
adjust_managed_page_count(page, -1);
scrub_page(page);
list_add(&page->lru, &pages);
}
/*
* Ensure that ballooned highmem pages don't have kmaps.
*
* Do this before changing the p2m as kmap_flush_unused()
* reads PTEs to obtain pages (and hence needs the original
* p2m entry).
*/
kmap_flush_unused();
/*
* Setup the frame, update direct mapping, invalidate P2M,
* and add to balloon.
*/
i = 0;
list_for_each_entry_safe(page, tmp, &pages, lru) {
/* XENMEM_decrease_reservation requires a GFN */
frame_list[i++] = xen_page_to_gfn(page);
#ifdef CONFIG_XEN_HAVE_PVMMU
/*
* We don't support PV MMU when Linux and Xen is using
* different page granularity.
*/
BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
unsigned long pfn = page_to_pfn(page);
if (!PageHighMem(page)) {
ret = HYPERVISOR_update_va_mapping(
(unsigned long)__va(pfn << PAGE_SHIFT),
__pte_ma(0), 0);
BUG_ON(ret);
}
__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
}
#endif
list_del(&page->lru);
balloon_append(page);
}
flush_tlb_all();
set_xen_guest_handle(reservation.extent_start, frame_list);
reservation.nr_extents = nr_pages;
ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
BUG_ON(ret != nr_pages);
balloon_stats.current_pages -= nr_pages;
return state;
}
/*
* As this is a work item it is guaranteed to run as a single instance only.
* We may of course race updates of the target counts (which are protected
* by the balloon lock), or with changes to the Xen hard limit, but we will
* recover from these in time.
*/
static void balloon_process(struct work_struct *work)
{
enum bp_state state = BP_DONE;
long credit;
do {
mutex_lock(&balloon_mutex);
credit = current_credit();
if (credit > 0) {
if (balloon_is_inflated())
state = increase_reservation(credit);
else
state = reserve_additional_memory();
}
if (credit < 0)
state = decrease_reservation(-credit, GFP_BALLOON);
state = update_schedule(state);
mutex_unlock(&balloon_mutex);
cond_resched();
} while (credit && state == BP_DONE);
/* Schedule more work if there is some still to be done. */
if (state == BP_EAGAIN)
schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ);
}
/* Resets the Xen limit, sets new target, and kicks off processing. */
void balloon_set_new_target(unsigned long target)
{
/* No need for lock. Not read-modify-write updates. */
balloon_stats.target_pages = target;
schedule_delayed_work(&balloon_worker, 0);
}
EXPORT_SYMBOL_GPL(balloon_set_new_target);
static int add_ballooned_pages(int nr_pages)
{
enum bp_state st;
if (xen_hotplug_unpopulated) {
st = reserve_additional_memory();
if (st != BP_ECANCELED) {
mutex_unlock(&balloon_mutex);
wait_event(balloon_wq,
!list_empty(&ballooned_pages));
mutex_lock(&balloon_mutex);
return 0;
}
}
st = decrease_reservation(nr_pages, GFP_USER);
if (st != BP_DONE)
return -ENOMEM;
return 0;
}
/**
* alloc_xenballooned_pages - get pages that have been ballooned out
* @nr_pages: Number of pages to get
* @pages: pages returned
* @return 0 on success, error otherwise
*/
int alloc_xenballooned_pages(int nr_pages, struct page **pages)
{
int pgno = 0;
struct page *page;
int ret;
mutex_lock(&balloon_mutex);
balloon_stats.target_unpopulated += nr_pages;
while (pgno < nr_pages) {
page = balloon_retrieve(true);
if (page) {
pages[pgno++] = page;
#ifdef CONFIG_XEN_HAVE_PVMMU
/*
* We don't support PV MMU when Linux and Xen is using
* different page granularity.
*/
BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
ret = xen_alloc_p2m_entry(page_to_pfn(page));
if (ret < 0)
goto out_undo;
}
#endif
} else {
ret = add_ballooned_pages(nr_pages - pgno);
if (ret < 0)
goto out_undo;
}
}
mutex_unlock(&balloon_mutex);
return 0;
out_undo:
mutex_unlock(&balloon_mutex);
free_xenballooned_pages(pgno, pages);
return ret;
}
EXPORT_SYMBOL(alloc_xenballooned_pages);
/**
* free_xenballooned_pages - return pages retrieved with get_ballooned_pages
* @nr_pages: Number of pages
* @pages: pages to return
*/
void free_xenballooned_pages(int nr_pages, struct page **pages)
{
int i;
mutex_lock(&balloon_mutex);
for (i = 0; i < nr_pages; i++) {
if (pages[i])
balloon_append(pages[i]);
}
balloon_stats.target_unpopulated -= nr_pages;
/* The balloon may be too large now. Shrink it if needed. */
if (current_credit())
schedule_delayed_work(&balloon_worker, 0);
mutex_unlock(&balloon_mutex);
}
EXPORT_SYMBOL(free_xenballooned_pages);
#ifdef CONFIG_XEN_PV
static void __init balloon_add_region(unsigned long start_pfn,
unsigned long pages)
{
unsigned long pfn, extra_pfn_end;
struct page *page;
/*
* If the amount of usable memory has been limited (e.g., with
* the 'mem' command line parameter), don't add pages beyond
* this limit.
*/
extra_pfn_end = min(max_pfn, start_pfn + pages);
for (pfn = start_pfn; pfn < extra_pfn_end; pfn++) {
page = pfn_to_page(pfn);
/* totalram_pages and totalhigh_pages do not
include the boot-time balloon extension, so
don't subtract from it. */
__balloon_append(page);
}
balloon_stats.total_pages += extra_pfn_end - start_pfn;
}
#endif
static int __init balloon_init(void)
{
if (!xen_domain())
return -ENODEV;
pr_info("Initialising balloon driver\n");
#ifdef CONFIG_XEN_PV
balloon_stats.current_pages = xen_pv_domain()
? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
: get_num_physpages();
#else
balloon_stats.current_pages = get_num_physpages();
#endif
balloon_stats.target_pages = balloon_stats.current_pages;
balloon_stats.balloon_low = 0;
balloon_stats.balloon_high = 0;
balloon_stats.total_pages = balloon_stats.current_pages;
balloon_stats.schedule_delay = 1;
balloon_stats.max_schedule_delay = 32;
balloon_stats.retry_count = 1;
balloon_stats.max_retry_count = RETRY_UNLIMITED;
#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
set_online_page_callback(&xen_online_page);
register_memory_notifier(&xen_memory_nb);
register_sysctl_table(xen_root);
arch_xen_balloon_init(&hostmem_resource);
#endif
#ifdef CONFIG_XEN_PV
{
int i;
/*
* Initialize the balloon with pages from the extra memory
* regions (see arch/x86/xen/setup.c).
*/
for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++)
if (xen_extra_mem[i].n_pfns)
balloon_add_region(xen_extra_mem[i].start_pfn,
xen_extra_mem[i].n_pfns);
}
#endif
/* Init the xen-balloon driver. */
xen_balloon_init();
return 0;
}
subsys_initcall(balloon_init);