xen/21453-shadow-avoid-remove-all-after-teardown.patch

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# HG changeset patch
# User Keir Fraser <keir.fraser@citrix.com>
# Date 1274857281 -3600
# Node ID 5addb6cb16fd64c664b1e3dd335c76b3426e05e9
# Parent 459f35d8cac4f19e6eae0a7396f6c97e20ae955c
x86 shadow: Avoid remove-all-shadows after shadow teardown
If dom0 alters the p2m of a domain that's being destroyed, we can end
up doing a remove-all-shadows after the shadow hash table has been
freed. Since no hash table implies no shadows, just return
immediately.
Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>
--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -2173,8 +2173,13 @@ static void hash_foreach(struct vcpu *v,
struct domain *d = v->domain;
struct page_info *x;
- /* Say we're here, to stop hash-lookups reordering the chains */
ASSERT(shadow_locked_by_me(d));
+
+ /* Can be called via p2m code &c after shadow teardown. */
+ if ( unlikely(!d->arch.paging.shadow.hash_table) )
+ return;
+
+ /* Say we're here, to stop hash-lookups reordering the chains */
ASSERT(d->arch.paging.shadow.hash_walking == 0);
d->arch.paging.shadow.hash_walking = 1;