| Message ID | 20221007221644.138355-1-jmattson@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86: Advertise that the SMM_CTL MSR is not supported | expand |
On Fri, Oct 07, 2022, Jim Mattson wrote: > CPUID.80000021H:EAX[bit 9] indicates that the SMM_CTL MSR (0xc0010116) > is not supported. This defeature can be advertised by > KVM_GET_SUPPORTED_CPUID regardless of whether or not the host > enumerates it. Might be worth noting that KVM will only enumerate the bit if the host happens to have a max extend leaf > 80000021. > > Signed-off-by: Jim Mattson <jmattson@google.com> > --- > arch/x86/kvm/cpuid.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 2796dde06302..b748fac2ae37 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -1199,8 +1199,12 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) > * Other defined bits are for MSRs that KVM does not expose: > * EAX 3 SPCL, SMM page configuration lock > * EAX 13 PCMSR, Prefetch control MSR > + * > + * KVM doesn't support SMM_CTL. > + * EAX 9 SMM_CTL MSR is not supported > */ > entry->eax &= BIT(0) | BIT(2) | BIT(6); I don't suppose I can bribe you to add a kvm_only_cpuid_leafs entry for these? :-) > + entry->eax |= BIT(9); > if (static_cpu_has(X86_FEATURE_LFENCE_RDTSC)) > entry->eax |= BIT(2); > if (!static_cpu_has_bug(X86_BUG_NULL_SEG)) > -- > 2.38.0.rc1.362.ged0d419d3c-goog >
On Fri, Oct 07, 2022, Sean Christopherson wrote: > On Fri, Oct 07, 2022, Jim Mattson wrote: > > CPUID.80000021H:EAX[bit 9] indicates that the SMM_CTL MSR (0xc0010116) > > is not supported. This defeature can be advertised by > > KVM_GET_SUPPORTED_CPUID regardless of whether or not the host > > enumerates it. > > Might be worth noting that KVM will only enumerate the bit if the host happens to > have a max extend leaf > 80000021. > > > > Signed-off-by: Jim Mattson <jmattson@google.com> > > --- > > arch/x86/kvm/cpuid.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > > index 2796dde06302..b748fac2ae37 100644 > > --- a/arch/x86/kvm/cpuid.c > > +++ b/arch/x86/kvm/cpuid.c > > @@ -1199,8 +1199,12 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) > > * Other defined bits are for MSRs that KVM does not expose: > > * EAX 3 SPCL, SMM page configuration lock > > * EAX 13 PCMSR, Prefetch control MSR > > + * > > + * KVM doesn't support SMM_CTL. > > + * EAX 9 SMM_CTL MSR is not supported > > */ > > entry->eax &= BIT(0) | BIT(2) | BIT(6); > > I don't suppose I can bribe you to add a kvm_only_cpuid_leafs entry for these? :-) Ha! Someone else must have heard me whining :-) https://lore.kernel.org/all/20221129235816.188737-5-kim.phillips@amd.com
On 10/8/22 00:27, Sean Christopherson wrote: >> CPUID.80000021H:EAX[bit 9] indicates that the SMM_CTL MSR (0xc0010116) >> is not supported. This defeature can be advertised by >> KVM_GET_SUPPORTED_CPUID regardless of whether or not the host >> enumerates it. > Might be worth noting that KVM will only enumerate the bit if the host happens to > have a max extend leaf > 80000021. Actually 0x8000001d, because 0x80000021 is a synthetic leaf (the only one of its kind). Unfortunately we cannot synthesize 0x80000021 unconditionally due to a preexisting bug in QEMU. :( Paolo
On 10/8/22 00:16, Jim Mattson wrote: > CPUID.80000021H:EAX[bit 9] indicates that the SMM_CTL MSR (0xc0010116) > is not supported. This defeature can be advertised by > KVM_GET_SUPPORTED_CPUID regardless of whether or not the host > enumerates it. > > Signed-off-by: Jim Mattson <jmattson@google.com> > --- > arch/x86/kvm/cpuid.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 2796dde06302..b748fac2ae37 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -1199,8 +1199,12 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) > * Other defined bits are for MSRs that KVM does not expose: > * EAX 3 SPCL, SMM page configuration lock > * EAX 13 PCMSR, Prefetch control MSR > + * > + * KVM doesn't support SMM_CTL. > + * EAX 9 SMM_CTL MSR is not supported > */ > entry->eax &= BIT(0) | BIT(2) | BIT(6); > + entry->eax |= BIT(9); > if (static_cpu_has(X86_FEATURE_LFENCE_RDTSC)) > entry->eax |= BIT(2); > if (!static_cpu_has_bug(X86_BUG_NULL_SEG)) Queued, thanks. Negative features suck, though. Paolo
On Fri, Dec 02, 2022, Paolo Bonzini wrote: > On 10/8/22 00:16, Jim Mattson wrote: > > CPUID.80000021H:EAX[bit 9] indicates that the SMM_CTL MSR (0xc0010116) > > is not supported. This defeature can be advertised by > > KVM_GET_SUPPORTED_CPUID regardless of whether or not the host > > enumerates it. > > > > Signed-off-by: Jim Mattson <jmattson@google.com> > > --- > > arch/x86/kvm/cpuid.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > > index 2796dde06302..b748fac2ae37 100644 > > --- a/arch/x86/kvm/cpuid.c > > +++ b/arch/x86/kvm/cpuid.c > > @@ -1199,8 +1199,12 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) > > * Other defined bits are for MSRs that KVM does not expose: > > * EAX 3 SPCL, SMM page configuration lock > > * EAX 13 PCMSR, Prefetch control MSR > > + * > > + * KVM doesn't support SMM_CTL. > > + * EAX 9 SMM_CTL MSR is not supported > > */ > > entry->eax &= BIT(0) | BIT(2) | BIT(6); > > + entry->eax |= BIT(9); > > if (static_cpu_has(X86_FEATURE_LFENCE_RDTSC)) > > entry->eax |= BIT(2); > > if (!static_cpu_has_bug(X86_BUG_NULL_SEG)) > > Queued, thanks. Negative features suck, though. LOL, you and Jim should start a club, Jim's had a few good rants on negative features :-)
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 2796dde06302..b748fac2ae37 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -1199,8 +1199,12 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) * Other defined bits are for MSRs that KVM does not expose: * EAX 3 SPCL, SMM page configuration lock * EAX 13 PCMSR, Prefetch control MSR + * + * KVM doesn't support SMM_CTL. + * EAX 9 SMM_CTL MSR is not supported */ entry->eax &= BIT(0) | BIT(2) | BIT(6); + entry->eax |= BIT(9); if (static_cpu_has(X86_FEATURE_LFENCE_RDTSC)) entry->eax |= BIT(2); if (!static_cpu_has_bug(X86_BUG_NULL_SEG))
CPUID.80000021H:EAX[bit 9] indicates that the SMM_CTL MSR (0xc0010116) is not supported. This defeature can be advertised by KVM_GET_SUPPORTED_CPUID regardless of whether or not the host enumerates it. Signed-off-by: Jim Mattson <jmattson@google.com> --- arch/x86/kvm/cpuid.c | 4 ++++ 1 file changed, 4 insertions(+)