| Message ID | 20210424004645.3950558-4-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86: vCPU RESET/INIT fixes and consolidation | expand |
On Fri, Apr 23, 2021 at 5:47 PM Sean Christopherson <seanjc@google.com> wrote: > > Do not allow an inexact CPUID "match" when querying the guest's CPUID.0x1 > to stuff EDX during INIT. In the common case, where the guest CPU model > is an AMD variant, allowing an inexact match is a nop since KVM doesn't > emulate Intel's goofy "out-of-range" logic for AMD and Hygon. If the > vCPU model happens to be an Intel variant, an inexact match is possible > if and only if the max CPUID leaf is precisely '0'. Aside from the fact > that there's probably no CPU in existence with a single CPUID leaf, if > the max CPUID leaf is '0', that means that CPUID.0.EAX is '0', and thus > an inexact match for CPUID.0x1.EAX will also yield '0'. > > So, with lots of twisty logic, no functional change intended. > > Signed-off-by: Sean Christopherson <seanjc@google.com> Reviewed-by: Reiji Watanabe <reijiw@google.com>
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 14ff7f0963e9..b9e3229ddc27 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -1299,7 +1299,7 @@ static void svm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) } init_vmcb(vcpu); - kvm_cpuid(vcpu, &eax, &dummy, &dummy, &dummy, false); + kvm_cpuid(vcpu, &eax, &dummy, &dummy, &dummy, true); kvm_rdx_write(vcpu, eax); if (kvm_vcpu_apicv_active(vcpu) && !init_event)
Do not allow an inexact CPUID "match" when querying the guest's CPUID.0x1 to stuff EDX during INIT. In the common case, where the guest CPU model is an AMD variant, allowing an inexact match is a nop since KVM doesn't emulate Intel's goofy "out-of-range" logic for AMD and Hygon. If the vCPU model happens to be an Intel variant, an inexact match is possible if and only if the max CPUID leaf is precisely '0'. Aside from the fact that there's probably no CPU in existence with a single CPUID leaf, if the max CPUID leaf is '0', that means that CPUID.0.EAX is '0', and thus an inexact match for CPUID.0x1.EAX will also yield '0'. So, with lots of twisty logic, no functional change intended. Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/svm/svm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)