Messages in this thread | | | Date | Thu, 20 Jan 2022 14:17:17 +0000 | Subject | Re: [PATCH 2/9] Revert "KVM: SVM: avoid infinite loop on NPF from bad address" | From | Liam Merwick <> |
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On 20/01/2022 01:07, Sean Christopherson wrote: > Revert a completely broken check on an "invalid" RIP in SVM's workaround > for the DecodeAssists SMAP errata. kvm_vcpu_gfn_to_memslot() obviously > expects a gfn, i.e. operates in the guest physical address space, whereas > RIP is a virtual (not even linear) address. The "fix" worked for the > problematic KVM selftest because the test identity mapped RIP. > > Fully revert the hack instead of trying to translate RIP to a GPA, as the > non-SEV case is now handled earlier, and KVM cannot access guest page > tables to translate RIP. > > This reverts commit e72436bc3a5206f95bb384e741154166ddb3202e. > > Fixes: e72436bc3a52 ("KVM: SVM: avoid infinite loop on NPF from bad address") > Reported-by: Liam Merwick <liam.merwick@oracle.com> > Cc: stable@vger.kernel.org > Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
> --- > arch/x86/kvm/svm/svm.c | 7 ------- > virt/kvm/kvm_main.c | 1 - > 2 files changed, 8 deletions(-) > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index aa1649b8cd8f..85703145eb0a 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -4311,13 +4311,6 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, void *insn, int i > if (likely(!insn || insn_len)) > return true; > > - /* > - * If RIP is invalid, go ahead with emulation which will cause an > - * internal error exit. > - */ > - if (!kvm_vcpu_gfn_to_memslot(vcpu, kvm_rip_read(vcpu) >> PAGE_SHIFT)) > - return true; > - > cr4 = kvm_read_cr4(vcpu); > smep = cr4 & X86_CR4_SMEP; > smap = cr4 & X86_CR4_SMAP; > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 5a1164483e6c..0bacecda79cf 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -2248,7 +2248,6 @@ struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn > > return NULL; > } > -EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_memslot); > > bool kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn) > {
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