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authorAvi Kivity <avi@qumranet.com>2008-06-12 16:54:41 +0300
committerAvi Kivity <avi@qumranet.com>2008-06-24 12:20:12 +0300
commit6bf6a9532fd03ad719f0c86654f16ef777b78fc6 (patch)
tree4865d4cd48c98c5425218c5d8289367bd16c4105
parent3094538739415a9225afd2a6c78cb0fe1c1f641b (diff)
KVM: MMU: Fix oops on guest userspace access to guest pagetable
KVM has a heuristic to unshadow guest pagetables when userspace accesses them, on the assumption that most guests do not allow userspace to access pagetables directly. Unfortunately, in addition to unshadowing the pagetables, it also oopses. This never triggers on ordinary guests since sane OSes will clear the pagetables before assigning them to userspace, which will trigger the flood heuristic, unshadowing the pagetables before the first userspace access. One particular guest, though (Xenner) will run the kernel in userspace, triggering the oops. Since the heuristic is incorrect in this case, we can simply remove it. Signed-off-by: Avi Kivity <avi@qumranet.com>
-rw-r--r--arch/x86/kvm/mmu.c6
1 files changed, 0 insertions, 6 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index baa6503894d..7e7c3969f7a 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1083,10 +1083,6 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *shadow_pte,
struct kvm_mmu_page *shadow;
spte |= PT_WRITABLE_MASK;
- if (user_fault) {
- mmu_unshadow(vcpu->kvm, gfn);
- goto unshadowed;
- }
shadow = kvm_mmu_lookup_page(vcpu->kvm, gfn);
if (shadow ||
@@ -1103,8 +1099,6 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *shadow_pte,
}
}
-unshadowed:
-
if (pte_access & ACC_WRITE_MASK)
mark_page_dirty(vcpu->kvm, gfn);