From ad7dc69aeb23138cc23c406cac25003b97e8ee17 Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Fri, 22 Feb 2019 17:45:01 +0100 Subject: x86/kvm/mmu: fix switch between root and guest MMUs Commit 14c07ad89f4d ("x86/kvm/mmu: introduce guest_mmu") brought one subtle change: previously, when switching back from L2 to L1, we were resetting MMU hooks (like mmu->get_cr3()) in kvm_init_mmu() called from nested_vmx_load_cr3() and now we do that in nested_ept_uninit_mmu_context() when we re-target vcpu->arch.mmu pointer. The change itself looks logical: if nested_ept_init_mmu_context() changes something than nested_ept_uninit_mmu_context() restores it back. There is, however, one thing: the following call chain: nested_vmx_load_cr3() kvm_mmu_new_cr3() __kvm_mmu_new_cr3() fast_cr3_switch() cached_root_available() now happens with MMU hooks pointing to the new MMU (root MMU in our case) while previously it was happening with the old one. cached_root_available() tries to stash current root but it is incorrect to read current CR3 with mmu->get_cr3(), we need to use old_mmu->get_cr3() which in case we're switching from L2 to L1 is guest_mmu. (BTW, in shadow page tables case this is a non-issue because we don't switch MMU). While we could've tried to guess that we're switching between MMUs and call the right ->get_cr3() from cached_root_available() this seems to be overly complicated. Instead, just stash the corresponding CR3 when setting root_hpa and make cached_root_available() use the stashed value. Fixes: 14c07ad89f4d ("x86/kvm/mmu: introduce guest_mmu") Signed-off-by: Vitaly Kuznetsov Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/mmu.c | 17 +++++++++++++---- 2 files changed, 14 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 4660ce90de7f..593e17b7797e 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -397,6 +397,7 @@ struct kvm_mmu { void (*update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, u64 *spte, const void *pte); hpa_t root_hpa; + gpa_t root_cr3; union kvm_mmu_role mmu_role; u8 root_level; u8 shadow_root_level; diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index da9c42349b1f..6e62ed3852ac 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3555,6 +3555,7 @@ void kvm_mmu_free_roots(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, &invalid_list); mmu->root_hpa = INVALID_PAGE; } + mmu->root_cr3 = 0; } kvm_mmu_commit_zap_page(vcpu->kvm, &invalid_list); @@ -3610,6 +3611,7 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu) vcpu->arch.mmu->root_hpa = __pa(vcpu->arch.mmu->pae_root); } else BUG(); + vcpu->arch.mmu->root_cr3 = vcpu->arch.mmu->get_cr3(vcpu); return 0; } @@ -3618,10 +3620,11 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) { struct kvm_mmu_page *sp; u64 pdptr, pm_mask; - gfn_t root_gfn; + gfn_t root_gfn, root_cr3; int i; - root_gfn = vcpu->arch.mmu->get_cr3(vcpu) >> PAGE_SHIFT; + root_cr3 = vcpu->arch.mmu->get_cr3(vcpu); + root_gfn = root_cr3 >> PAGE_SHIFT; if (mmu_check_root(vcpu, root_gfn)) return 1; @@ -3646,7 +3649,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) ++sp->root_count; spin_unlock(&vcpu->kvm->mmu_lock); vcpu->arch.mmu->root_hpa = root; - return 0; + goto set_root_cr3; } /* @@ -3712,6 +3715,9 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) vcpu->arch.mmu->root_hpa = __pa(vcpu->arch.mmu->lm_root); } +set_root_cr3: + vcpu->arch.mmu->root_cr3 = root_cr3; + return 0; } @@ -4163,7 +4169,7 @@ static bool cached_root_available(struct kvm_vcpu *vcpu, gpa_t new_cr3, struct kvm_mmu_root_info root; struct kvm_mmu *mmu = vcpu->arch.mmu; - root.cr3 = mmu->get_cr3(vcpu); + root.cr3 = mmu->root_cr3; root.hpa = mmu->root_hpa; for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) { @@ -4176,6 +4182,7 @@ static bool cached_root_available(struct kvm_vcpu *vcpu, gpa_t new_cr3, } mmu->root_hpa = root.hpa; + mmu->root_cr3 = root.cr3; return i < KVM_MMU_NUM_PREV_ROOTS; } @@ -5516,11 +5523,13 @@ int kvm_mmu_create(struct kvm_vcpu *vcpu) vcpu->arch.walk_mmu = &vcpu->arch.root_mmu; vcpu->arch.root_mmu.root_hpa = INVALID_PAGE; + vcpu->arch.root_mmu.root_cr3 = 0; vcpu->arch.root_mmu.translate_gpa = translate_gpa; for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) vcpu->arch.root_mmu.prev_roots[i] = KVM_MMU_ROOT_INFO_INVALID; vcpu->arch.guest_mmu.root_hpa = INVALID_PAGE; + vcpu->arch.guest_mmu.root_cr3 = 0; vcpu->arch.guest_mmu.translate_gpa = translate_gpa; for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) vcpu->arch.guest_mmu.prev_roots[i] = KVM_MMU_ROOT_INFO_INVALID; -- cgit v1.2.3