From 2bad07ce28a0f61c1e776f99aa05f85e4e689e24 Mon Sep 17 00:00:00 2001
From: David Vrabel <david.vrabel@citrix.com>
Date: Wed, 11 Sep 2013 17:45:44 +0000
Subject: [PATCH] xen/balloon: ensure preemption is disabled when using a
scratch page
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>
---
drivers/xen/balloon.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 3101cf6daf56..4a43bc31ed3c 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -380,6 +380,7 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
enum bp_state state = BP_DONE;
unsigned long pfn, i;
struct page *page;
+ struct page *scratch_page;
int ret;
struct xen_memory_reservation reservation = {
.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))
nr_pages = ARRAY_SIZE(frame_list);
+ scratch_page = get_balloon_scratch_page();
+
for (i = 0; i < nr_pages; i++) {
page = alloc_page(gfp);
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)) {
ret = HYPERVISOR_update_va_mapping(
(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);
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]);
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
unsigned long p;
- struct page *pg;
- pg = __get_cpu_var(balloon_scratch_page);
- p = page_to_pfn(pg);
+ p = page_to_pfn(scratch_page);
__set_phys_to_machine(pfn, pfn_to_mfn(p));
}
balloon_append(pfn_to_page(pfn));
}
+ put_balloon_scratch_page();
+
set_xen_guest_handle(reservation.extent_start, frame_list);
reservation.nr_extents = nr_pages;
ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
--
2.20.1