From eb45fda45f915c7ca3e81e005e853cb770da2642 Mon Sep 17 00:00:00 2001
From: Marcelo Tosatti <mtosatti@redhat.com>
Date: Mon, 25 Oct 2010 11:58:22 -0200
Subject: [PATCH] KVM: MMU: fix rmap_remove on non present sptes
drop_spte should not attempt to rmap_remove a non present shadow pte.
This fixes a BUG_ON seen on kvm-autotest.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Reported-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
arch/x86/kvm/mmu.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 908ea5464a51..fb8b376bf28c 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -720,7 +720,7 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
}
}
-static void set_spte_track_bits(u64 *sptep, u64 new_spte)
+static int set_spte_track_bits(u64 *sptep, u64 new_spte)
{
pfn_t pfn;
u64 old_spte = *sptep;
@@ -731,19 +731,20 @@ static void set_spte_track_bits(u64 *sptep, u64 new_spte)
old_spte = __xchg_spte(sptep, new_spte);
if (!is_rmap_spte(old_spte))
- return;
+ return 0;
pfn = spte_to_pfn(old_spte);
if (!shadow_accessed_mask || old_spte & shadow_accessed_mask)
kvm_set_pfn_accessed(pfn);
if (!shadow_dirty_mask || (old_spte & shadow_dirty_mask))
kvm_set_pfn_dirty(pfn);
+ return 1;
}
static void drop_spte(struct kvm *kvm, u64 *sptep, u64 new_spte)
{
- set_spte_track_bits(sptep, new_spte);
- rmap_remove(kvm, sptep);
+ if (set_spte_track_bits(sptep, new_spte))
+ rmap_remove(kvm, sptep);
}
static u64 *rmap_next(struct kvm *kvm, unsigned long *rmapp, u64 *spte)
--
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