Messages in this thread | | | From | Kyle Huey <> | Date | Wed, 16 Nov 2016 17:59:30 -0800 | Subject | Re: [PATCH v11 7/7] KVM: x86: virtualize cpuid faulting |
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On Wed, Nov 16, 2016 at 12:42 PM, Paolo Bonzini <pbonzini@redhat.com> wrote: >> On Fri, Nov 11, 2016 at 12:54 PM, Nadav Amit <nadav.amit@gmail.com> wrote: >> > >> >> On Nov 10, 2016, at 3:40 PM, Kyle Huey <me@kylehuey.com> wrote: >> >> >> >> Hardware support for faulting on the cpuid instruction is not required to >> >> emulate it, because cpuid triggers a VM exit anyways. KVM handles the >> >> relevant >> >> MSRs (MSR_PLATFORM_INFO and MSR_MISC_FEATURES_ENABLE) and upon a >> >> cpuid-induced VM exit checks the cpuid faulting state and the CPL. >> >> kvm_require_cpl is even kind enough to inject the GP fault for us. >> > >> > I think that for consistency you should also revise em_cpuid() of KVM >> > instruction emulator. Otherwise it may be a potential security >> > hazard (as far fetched as it currently seems). >> >> Hmm, ok. Do you know how I can test this code path? > > Try this patch (untested!)
Heh, yes, that would do it. Thanks!
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index 5382b82462fc..06d940a7c9fa 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -5868,8 +5868,7 @@ static void vmx_set_dr7(struct kvm_vcpu *vcpu, unsigned long val) > > static int handle_cpuid(struct kvm_vcpu *vcpu) > { > - kvm_emulate_cpuid(vcpu); > - return 1; > + return emulate_instruction(vcpu, 0) == EMULATE_DONE; > } > > static int handle_rdmsr(struct kvm_vcpu *vcpu) > > Paolo
- Kyle
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