* [PATCH] KVM: x86: Advertise that the SMM_CTL MSR is not supported
@ 2022-10-07 22:16 Jim Mattson
2022-10-07 22:27 ` Sean Christopherson
2022-12-02 18:50 ` Paolo Bonzini
0 siblings, 2 replies; 6+ messages in thread
From: Jim Mattson @ 2022-10-07 22:16 UTC (permalink / raw)
To: kvm, pbonzini, seanjc; +Cc: Jim Mattson
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))
--
2.38.0.rc1.362.ged0d419d3c-goog
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: x86: Advertise that the SMM_CTL MSR is not supported
2022-10-07 22:16 [PATCH] KVM: x86: Advertise that the SMM_CTL MSR is not supported Jim Mattson
@ 2022-10-07 22:27 ` Sean Christopherson
2022-12-01 0:08 ` Sean Christopherson
2022-12-02 18:45 ` Paolo Bonzini
2022-12-02 18:50 ` Paolo Bonzini
1 sibling, 2 replies; 6+ messages in thread
From: Sean Christopherson @ 2022-10-07 22:27 UTC (permalink / raw)
To: Jim Mattson; +Cc: kvm, pbonzini
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
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: x86: Advertise that the SMM_CTL MSR is not supported
2022-10-07 22:27 ` Sean Christopherson
@ 2022-12-01 0:08 ` Sean Christopherson
2022-12-02 18:45 ` Paolo Bonzini
1 sibling, 0 replies; 6+ messages in thread
From: Sean Christopherson @ 2022-12-01 0:08 UTC (permalink / raw)
To: Jim Mattson; +Cc: kvm, pbonzini
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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: x86: Advertise that the SMM_CTL MSR is not supported
2022-10-07 22:27 ` Sean Christopherson
2022-12-01 0:08 ` Sean Christopherson
@ 2022-12-02 18:45 ` Paolo Bonzini
1 sibling, 0 replies; 6+ messages in thread
From: Paolo Bonzini @ 2022-12-02 18:45 UTC (permalink / raw)
To: Sean Christopherson, Jim Mattson; +Cc: kvm
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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: x86: Advertise that the SMM_CTL MSR is not supported
2022-10-07 22:16 [PATCH] KVM: x86: Advertise that the SMM_CTL MSR is not supported Jim Mattson
2022-10-07 22:27 ` Sean Christopherson
@ 2022-12-02 18:50 ` Paolo Bonzini
2022-12-02 18:58 ` Sean Christopherson
1 sibling, 1 reply; 6+ messages in thread
From: Paolo Bonzini @ 2022-12-02 18:50 UTC (permalink / raw)
To: Jim Mattson, kvm, seanjc
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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: x86: Advertise that the SMM_CTL MSR is not supported
2022-12-02 18:50 ` Paolo Bonzini
@ 2022-12-02 18:58 ` Sean Christopherson
0 siblings, 0 replies; 6+ messages in thread
From: Sean Christopherson @ 2022-12-02 18:58 UTC (permalink / raw)
To: Paolo Bonzini; +Cc: Jim Mattson, kvm
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 :-)
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-12-02 18:59 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2022-10-07 22:16 [PATCH] KVM: x86: Advertise that the SMM_CTL MSR is not supported Jim Mattson
2022-10-07 22:27 ` Sean Christopherson
2022-12-01 0:08 ` Sean Christopherson
2022-12-02 18:45 ` Paolo Bonzini
2022-12-02 18:50 ` Paolo Bonzini
2022-12-02 18:58 ` Sean Christopherson
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