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xen/balloon: ensure preemption is disabled when using a scratch page

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In decrease_reservation(), if the kernel is preempted between updating
the mapping and updating the p2m then they may end up using different
scratch pages.

Use get_balloon_scratch_page() and put_balloon_scratch_page() which use
get_cpu_var() and put_cpu_var() to correctly disable preemption.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Tested-by: Sander Eikelenboom <linux@eikelenboom.it>
This commit is contained in:
David Vrabel 2013-09-11 17:45:44 +00:00 committed by Stefano Stabellini
parent c3b7cb1fd8
commit 2bad07ce28
1 changed files with 7 additions and 4 deletions
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11
drivers/xen/balloon.c
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@ -380,6 +380,7 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
enum bp_state state = BP_DONE; enum bp_state state = BP_DONE;
unsigned long pfn, i; unsigned long pfn, i;
struct page *page; struct page *page;
struct page *scratch_page;
int ret; int ret;
struct xen_memory_reservation reservation = { struct xen_memory_reservation reservation = {
.address_bits = 0, .address_bits = 0,
@ -399,6 +400,8 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
if (nr_pages > ARRAY_SIZE(frame_list)) if (nr_pages > ARRAY_SIZE(frame_list))
nr_pages = ARRAY_SIZE(frame_list); nr_pages = ARRAY_SIZE(frame_list);
scratch_page = get_balloon_scratch_page();
for (i = 0; i < nr_pages; i++) { for (i = 0; i < nr_pages; i++) {
page = alloc_page(gfp); page = alloc_page(gfp);
if (page == NULL) { if (page == NULL) {
@ -416,7 +419,7 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
if (xen_pv_domain() && !PageHighMem(page)) { if (xen_pv_domain() && !PageHighMem(page)) {
ret = HYPERVISOR_update_va_mapping( ret = HYPERVISOR_update_va_mapping(
(unsigned long)__va(pfn << PAGE_SHIFT), (unsigned long)__va(pfn << PAGE_SHIFT),
pfn_pte(page_to_pfn(__get_cpu_var(balloon_scratch_page)), pfn_pte(page_to_pfn(scratch_page),
PAGE_KERNEL_RO), 0); PAGE_KERNEL_RO), 0);
BUG_ON(ret); BUG_ON(ret);
} }
@ -432,14 +435,14 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
pfn = mfn_to_pfn(frame_list[i]); pfn = mfn_to_pfn(frame_list[i]);
if (!xen_feature(XENFEAT_auto_translated_physmap)) { if (!xen_feature(XENFEAT_auto_translated_physmap)) {
unsigned long p; unsigned long p;
struct page *pg; p = page_to_pfn(scratch_page);
pg = __get_cpu_var(balloon_scratch_page);
p = page_to_pfn(pg);
__set_phys_to_machine(pfn, pfn_to_mfn(p)); __set_phys_to_machine(pfn, pfn_to_mfn(p));
} }
balloon_append(pfn_to_page(pfn)); balloon_append(pfn_to_page(pfn));
} }
put_balloon_scratch_page();
set_xen_guest_handle(reservation.extent_start, frame_list); set_xen_guest_handle(reservation.extent_start, frame_list);
reservation.nr_extents = nr_pages; reservation.nr_extents = nr_pages;
ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation); ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);