From f0f5933a1626c8df7b0bfd227819c66320fb4f0f Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Mon, 10 May 2010 12:09:56 +0300 Subject: [PATCH] KVM: MMU: Fix free memory accounting race in mmu_alloc_roots() We drop the mmu lock between freeing memory and allocating the roots; this allows some other vcpu to sneak in and allocate memory. While the race is benign (resulting only in temporary overallocation, not oom) it is simple and easy to fix by moving the freeing close to the allocation. Signed-off-by: Avi Kivity Signed-off-by: Marcelo Tosatti --- arch/x86/kvm/mmu.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 4a02dee..d7aebaf 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2094,6 +2094,7 @@ static int mmu_alloc_roots(struct kvm_vcpu *vcpu) root_gfn = 0; } spin_lock(&vcpu->kvm->mmu_lock); + kvm_mmu_free_some_pages(vcpu->kvm); sp = kvm_mmu_get_page(vcpu, root_gfn, 0, PT64_ROOT_LEVEL, direct, ACC_ALL, NULL); @@ -2124,6 +2125,7 @@ static int mmu_alloc_roots(struct kvm_vcpu *vcpu) root_gfn = i << 30; } spin_lock(&vcpu->kvm->mmu_lock); + kvm_mmu_free_some_pages(vcpu->kvm); sp = kvm_mmu_get_page(vcpu, root_gfn, i << 30, PT32_ROOT_LEVEL, direct, ACC_ALL, NULL); @@ -2496,9 +2498,6 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu) r = mmu_topup_memory_caches(vcpu); if (r) goto out; - spin_lock(&vcpu->kvm->mmu_lock); - kvm_mmu_free_some_pages(vcpu); - spin_unlock(&vcpu->kvm->mmu_lock); r = mmu_alloc_roots(vcpu); spin_lock(&vcpu->kvm->mmu_lock); mmu_sync_roots(vcpu); -- 2.7.4