From 6bf6a9532fd03ad719f0c86654f16ef777b78fc6 Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Thu, 12 Jun 2008 16:54:41 +0300 Subject: [PATCH] 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 --- arch/x86/kvm/mmu.c | 6 ------ 1 file changed, 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); -- 2.20.1