diff mbox series

[v3,5/8] KVM: x86/cpuid: Add X86_FEATURE_AMD_PMU_V2 as a KVM-only leaf entry

Message ID 20221111102645.82001-6-likexu@tencent.com (mailing list archive)
State New, archived
Headers show
Series KVM: x86: Add AMD Guest PerfMonV2 PMU support | expand

Commit Message

Like Xu Nov. 11, 2022, 10:26 a.m. UTC 
From: Like Xu <likexu@tencent.com>

Alias X86_FEATURE_AMD_PMU_V2 for feature AMD_PMU_V2 in KVM-only leafs that
aren't scattered by cpufeatures.h so that it can be used in KVM, e.g. to
query guest CPUID.  As a bonus, no translation is needed for these features
in __feature_translate().

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Like Xu <likexu@tencent.com>
---
 arch/x86/kvm/reverse_cpuid.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

Comments

Sean Christopherson Jan. 24, 2023, 7:47 p.m. UTC | #1 
On Fri, Nov 11, 2022, Like Xu wrote:
> From: Like Xu <likexu@tencent.com>
> 
> Alias X86_FEATURE_AMD_PMU_V2 for feature AMD_PMU_V2 in KVM-only leafs that
> aren't scattered by cpufeatures.h so that it can be used in KVM, e.g. to
> query guest CPUID.  As a bonus, no translation is needed for these features
> in __feature_translate().
> 
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Like Xu <likexu@tencent.com>
> ---
>  arch/x86/kvm/reverse_cpuid.h | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
> index a19d473d0184..7cfedb3e47c0 100644
> --- a/arch/x86/kvm/reverse_cpuid.h
> +++ b/arch/x86/kvm/reverse_cpuid.h
> @@ -13,6 +13,7 @@
>   */
>  enum kvm_only_cpuid_leafs {
>  	CPUID_12_EAX	 = NCAPINTS,
> +	CPUID_8000_0022_EAX,
>  	NR_KVM_CPU_CAPS,
>  
>  	NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
> @@ -23,7 +24,15 @@ enum kvm_only_cpuid_leafs {
>  /* Intel-defined SGX sub-features, CPUID level 0x12 (EAX). */
>  #define KVM_X86_FEATURE_SGX1		KVM_X86_FEATURE(CPUID_12_EAX, 0)
>  #define KVM_X86_FEATURE_SGX2		KVM_X86_FEATURE(CPUID_12_EAX, 1)
> +#define KVM_X86_FEATURE_AMD_PMU_V2	KVM_X86_FEATURE(CPUID_8000_0022_EAX, 0)
>  
> +/*
> + * Alias X86_FEATURE_* to the KVM variant for features in KVM-only leafs that
> + * aren't scattered by cpufeatures.h so that X86_FEATURE_* can be used in KVM,
> + * e.g. to query guest CPUID.  As a bonus, no translation is needed for these
> + * features in __feature_translate().
> + */
> +#define X86_FEATURE_AMD_PMU_V2      KVM_X86_FEATURE_AMD_PMU_V2

I gave you bad input earlier, for purely KVM-defined flags there's no need for an
intermediate KVM_X86_FEATURE_AMD_PMU_V2, this could simply be:

  #define X86_FEATURE_AMD_PMU_V2         KVM_X86_FEATURE(CPUID_8000_0022_EAX, 0)

That's a moot point though because, after much searching because I had a very hard
time believing the kernel wouldn't want to know about this flag, I found commit

  d6d0c7f681fd ("x86/cpufeatures: Add PerfMonV2 feature bit")

from nearly a year ago.  I.e. to avoid confusiong, this needs to be a scattered
flag, not a purely KVM flag.

---
 arch/x86/kvm/reverse_cpuid.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
index 4945456fd646..333e28b0a13c 100644
--- a/arch/x86/kvm/reverse_cpuid.h
+++ b/arch/x86/kvm/reverse_cpuid.h
@@ -15,6 +15,7 @@ enum kvm_only_cpuid_leafs {
 	CPUID_12_EAX	 = NCAPINTS,
 	CPUID_7_1_EDX,
 	CPUID_8000_0007_EDX,
+	CPUID_8000_0022_EAX,
 	NR_KVM_CPU_CAPS,
 
 	NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
@@ -47,6 +48,9 @@ enum kvm_only_cpuid_leafs {
 /* CPUID level 0x80000007 (EDX). */
 #define KVM_X86_FEATURE_CONSTANT_TSC	KVM_X86_FEATURE(CPUID_8000_0007_EDX, 8)
 
+/* CPUID level 0x80000022 (EAX) */
+#define KVM_X86_FEATURE_PERFMON_V2	KVM_X86_FEATURE(CPUID_8000_0022_EAX, 0)
+
 struct cpuid_reg {
 	u32 function;
 	u32 index;
@@ -73,6 +77,7 @@ static const struct cpuid_reg reverse_cpuid[] = {
 	[CPUID_8000_001F_EAX] = {0x8000001f, 0, CPUID_EAX},
 	[CPUID_7_1_EDX]       = {         7, 1, CPUID_EDX},
 	[CPUID_8000_0007_EDX] = {0x80000007, 0, CPUID_EDX},
+	[CPUID_8000_0022_EAX] = {0x80000022, 0, CPUID_EAX},
 };
 
 /*
@@ -107,6 +112,8 @@ static __always_inline u32 __feature_translate(int x86_feature)
 		return KVM_X86_FEATURE_SGX_EDECCSSA;
 	else if (x86_feature == X86_FEATURE_CONSTANT_TSC)
 		return KVM_X86_FEATURE_CONSTANT_TSC;
+	else if (x86_feature == X86_FEATURE_PERFMON_V2)
+		return KVM_X86_FEATURE_PERFMON_V2;
 
 	return x86_feature;
 }

base-commit: 5f3f3cc1279cd5cd52d301b97844bd3ce40c8020
--
Like Xu Feb. 6, 2023, 11:47 a.m. UTC | #2 
On 25/1/2023 3:47 am, Sean Christopherson wrote:
> On Fri, Nov 11, 2022, Like Xu wrote:
>> From: Like Xu <likexu@tencent.com>
>>
>> Alias X86_FEATURE_AMD_PMU_V2 for feature AMD_PMU_V2 in KVM-only leafs that
>> aren't scattered by cpufeatures.h so that it can be used in KVM, e.g. to
>> query guest CPUID.  As a bonus, no translation is needed for these features
>> in __feature_translate().
>>
>> Suggested-by: Sean Christopherson <seanjc@google.com>
>> Signed-off-by: Like Xu <likexu@tencent.com>
>> ---
>>   arch/x86/kvm/reverse_cpuid.h | 10 ++++++++++
>>   1 file changed, 10 insertions(+)
>>
>> diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
>> index a19d473d0184..7cfedb3e47c0 100644
>> --- a/arch/x86/kvm/reverse_cpuid.h
>> +++ b/arch/x86/kvm/reverse_cpuid.h
>> @@ -13,6 +13,7 @@
>>    */
>>   enum kvm_only_cpuid_leafs {
>>   	CPUID_12_EAX	 = NCAPINTS,
>> +	CPUID_8000_0022_EAX,
>>   	NR_KVM_CPU_CAPS,
>>   
>>   	NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
>> @@ -23,7 +24,15 @@ enum kvm_only_cpuid_leafs {
>>   /* Intel-defined SGX sub-features, CPUID level 0x12 (EAX). */
>>   #define KVM_X86_FEATURE_SGX1		KVM_X86_FEATURE(CPUID_12_EAX, 0)
>>   #define KVM_X86_FEATURE_SGX2		KVM_X86_FEATURE(CPUID_12_EAX, 1)
>> +#define KVM_X86_FEATURE_AMD_PMU_V2	KVM_X86_FEATURE(CPUID_8000_0022_EAX, 0)
>>   
>> +/*
>> + * Alias X86_FEATURE_* to the KVM variant for features in KVM-only leafs that
>> + * aren't scattered by cpufeatures.h so that X86_FEATURE_* can be used in KVM,
>> + * e.g. to query guest CPUID.  As a bonus, no translation is needed for these
>> + * features in __feature_translate().
>> + */
>> +#define X86_FEATURE_AMD_PMU_V2      KVM_X86_FEATURE_AMD_PMU_V2
> 
> I gave you bad input earlier, for purely KVM-defined flags there's no need for an
> intermediate KVM_X86_FEATURE_AMD_PMU_V2, this could simply be:
> 
>    #define X86_FEATURE_AMD_PMU_V2         KVM_X86_FEATURE(CPUID_8000_0022_EAX, 0)
> 
> That's a moot point though because, after much searching because I had a very hard
> time believing the kernel wouldn't want to know about this flag, I found commit
> 
>    d6d0c7f681fd ("x86/cpufeatures: Add PerfMonV2 feature bit")
> 
> from nearly a year ago.  I.e. to avoid confusiong, this needs to be a scattered
> flag, not a purely KVM flag.
> 
> ---
>   arch/x86/kvm/reverse_cpuid.h | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
> index 4945456fd646..333e28b0a13c 100644
> --- a/arch/x86/kvm/reverse_cpuid.h
> +++ b/arch/x86/kvm/reverse_cpuid.h
> @@ -15,6 +15,7 @@ enum kvm_only_cpuid_leafs {
>   	CPUID_12_EAX	 = NCAPINTS,
>   	CPUID_7_1_EDX,
>   	CPUID_8000_0007_EDX,
> +	CPUID_8000_0022_EAX,
>   	NR_KVM_CPU_CAPS,
>   
>   	NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
> @@ -47,6 +48,9 @@ enum kvm_only_cpuid_leafs {
>   /* CPUID level 0x80000007 (EDX). */
>   #define KVM_X86_FEATURE_CONSTANT_TSC	KVM_X86_FEATURE(CPUID_8000_0007_EDX, 8)
>   
> +/* CPUID level 0x80000022 (EAX) */
> +#define KVM_X86_FEATURE_PERFMON_V2	KVM_X86_FEATURE(CPUID_8000_0022_EAX, 0)

I'm very confused and is this the usage you want to see:

	kvm_cpu_cap_set(KVM_X86_FEATURE_PERFMON_V2)
	kvm_cpu_cap_has(KVM_X86_FEATURE_PERFMON_V2)
	guest_cpuid_has(vcpu, X86_FEATURE_PERFMON_V2)

? then what about X86_FEATURE_PERFMON_V2 ?

> +
>   struct cpuid_reg {
>   	u32 function;
>   	u32 index;
> @@ -73,6 +77,7 @@ static const struct cpuid_reg reverse_cpuid[] = {
>   	[CPUID_8000_001F_EAX] = {0x8000001f, 0, CPUID_EAX},
>   	[CPUID_7_1_EDX]       = {         7, 1, CPUID_EDX},
>   	[CPUID_8000_0007_EDX] = {0x80000007, 0, CPUID_EDX},
> +	[CPUID_8000_0022_EAX] = {0x80000022, 0, CPUID_EAX},
>   };
>   
>   /*
> @@ -107,6 +112,8 @@ static __always_inline u32 __feature_translate(int x86_feature)
>   		return KVM_X86_FEATURE_SGX_EDECCSSA;
>   	else if (x86_feature == X86_FEATURE_CONSTANT_TSC)
>   		return KVM_X86_FEATURE_CONSTANT_TSC;
> +	else if (x86_feature == X86_FEATURE_PERFMON_V2)
> +		return KVM_X86_FEATURE_PERFMON_V2;
>   
>   	return x86_feature;
>   }
> 
> base-commit: 5f3f3cc1279cd5cd52d301b97844bd3ce40c8020
Sean Christopherson Feb. 10, 2023, 1:32 a.m. UTC | #3 
On Mon, Feb 06, 2023, Like Xu wrote:
> On 25/1/2023 3:47 am, Sean Christopherson wrote:
> > On Fri, Nov 11, 2022, Like Xu wrote:
> > > From: Like Xu <likexu@tencent.com>
> > > 
> > > Alias X86_FEATURE_AMD_PMU_V2 for feature AMD_PMU_V2 in KVM-only leafs that
> > > aren't scattered by cpufeatures.h so that it can be used in KVM, e.g. to
> > > query guest CPUID.  As a bonus, no translation is needed for these features
> > > in __feature_translate().
> > > 
> > > Suggested-by: Sean Christopherson <seanjc@google.com>
> > > Signed-off-by: Like Xu <likexu@tencent.com>
> > > ---
> > >   arch/x86/kvm/reverse_cpuid.h | 10 ++++++++++
> > >   1 file changed, 10 insertions(+)
> > > 
> > > diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
> > > index a19d473d0184..7cfedb3e47c0 100644
> > > --- a/arch/x86/kvm/reverse_cpuid.h
> > > +++ b/arch/x86/kvm/reverse_cpuid.h
> > > @@ -13,6 +13,7 @@
> > >    */
> > >   enum kvm_only_cpuid_leafs {
> > >   	CPUID_12_EAX	 = NCAPINTS,
> > > +	CPUID_8000_0022_EAX,
> > >   	NR_KVM_CPU_CAPS,
> > >   	NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
> > > @@ -23,7 +24,15 @@ enum kvm_only_cpuid_leafs {
> > >   /* Intel-defined SGX sub-features, CPUID level 0x12 (EAX). */
> > >   #define KVM_X86_FEATURE_SGX1		KVM_X86_FEATURE(CPUID_12_EAX, 0)
> > >   #define KVM_X86_FEATURE_SGX2		KVM_X86_FEATURE(CPUID_12_EAX, 1)
> > > +#define KVM_X86_FEATURE_AMD_PMU_V2	KVM_X86_FEATURE(CPUID_8000_0022_EAX, 0)
> > > +/*
> > > + * Alias X86_FEATURE_* to the KVM variant for features in KVM-only leafs that
> > > + * aren't scattered by cpufeatures.h so that X86_FEATURE_* can be used in KVM,
> > > + * e.g. to query guest CPUID.  As a bonus, no translation is needed for these
> > > + * features in __feature_translate().
> > > + */
> > > +#define X86_FEATURE_AMD_PMU_V2      KVM_X86_FEATURE_AMD_PMU_V2
> > 
> > I gave you bad input earlier, for purely KVM-defined flags there's no need for an
> > intermediate KVM_X86_FEATURE_AMD_PMU_V2, this could simply be:
> > 
> >    #define X86_FEATURE_AMD_PMU_V2         KVM_X86_FEATURE(CPUID_8000_0022_EAX, 0)
> > 
> > That's a moot point though because, after much searching because I had a very hard
> > time believing the kernel wouldn't want to know about this flag, I found commit
> > 
> >    d6d0c7f681fd ("x86/cpufeatures: Add PerfMonV2 feature bit")
> > 
> > from nearly a year ago.  I.e. to avoid confusiong, this needs to be a scattered
> > flag, not a purely KVM flag.
> > 
> > ---
> >   arch/x86/kvm/reverse_cpuid.h | 7 +++++++
> >   1 file changed, 7 insertions(+)
> > 
> > diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
> > index 4945456fd646..333e28b0a13c 100644
> > --- a/arch/x86/kvm/reverse_cpuid.h
> > +++ b/arch/x86/kvm/reverse_cpuid.h
> > @@ -15,6 +15,7 @@ enum kvm_only_cpuid_leafs {
> >   	CPUID_12_EAX	 = NCAPINTS,
> >   	CPUID_7_1_EDX,
> >   	CPUID_8000_0007_EDX,
> > +	CPUID_8000_0022_EAX,
> >   	NR_KVM_CPU_CAPS,
> >   	NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
> > @@ -47,6 +48,9 @@ enum kvm_only_cpuid_leafs {
> >   /* CPUID level 0x80000007 (EDX). */
> >   #define KVM_X86_FEATURE_CONSTANT_TSC	KVM_X86_FEATURE(CPUID_8000_0007_EDX, 8)
> > +/* CPUID level 0x80000022 (EAX) */
> > +#define KVM_X86_FEATURE_PERFMON_V2	KVM_X86_FEATURE(CPUID_8000_0022_EAX, 0)
> 
> I'm very confused and is this the usage you want to see:
> 
> 	kvm_cpu_cap_set(KVM_X86_FEATURE_PERFMON_V2)
> 	kvm_cpu_cap_has(KVM_X86_FEATURE_PERFMON_V2)
> 	guest_cpuid_has(vcpu, X86_FEATURE_PERFMON_V2)
> 
> ?

No, all of those should just use X86_FEATURE_PERFMON_V2, i.e. the existing flag
from cpufeatures.h.

> then what about X86_FEATURE_PERFMON_V2 ?

Not sure I follow.  As above, it's scattered, thus KVM needs to redirect it to
the hardware-defined bit position, which is the role of __feature_translate()
and KVM_X86_FEATURE_PERFMON_V2.
diff mbox series

Patch

diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
index a19d473d0184..7cfedb3e47c0 100644
--- a/arch/x86/kvm/reverse_cpuid.h
+++ b/arch/x86/kvm/reverse_cpuid.h
@@ -13,6 +13,7 @@ 
  */
 enum kvm_only_cpuid_leafs {
 	CPUID_12_EAX	 = NCAPINTS,
+	CPUID_8000_0022_EAX,
 	NR_KVM_CPU_CAPS,
 
 	NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
@@ -23,7 +24,15 @@  enum kvm_only_cpuid_leafs {
 /* Intel-defined SGX sub-features, CPUID level 0x12 (EAX). */
 #define KVM_X86_FEATURE_SGX1		KVM_X86_FEATURE(CPUID_12_EAX, 0)
 #define KVM_X86_FEATURE_SGX2		KVM_X86_FEATURE(CPUID_12_EAX, 1)
+#define KVM_X86_FEATURE_AMD_PMU_V2	KVM_X86_FEATURE(CPUID_8000_0022_EAX, 0)
 
+/*
+ * Alias X86_FEATURE_* to the KVM variant for features in KVM-only leafs that
+ * aren't scattered by cpufeatures.h so that X86_FEATURE_* can be used in KVM,
+ * e.g. to query guest CPUID.  As a bonus, no translation is needed for these
+ * features in __feature_translate().
+ */
+#define X86_FEATURE_AMD_PMU_V2      KVM_X86_FEATURE_AMD_PMU_V2
 struct cpuid_reg {
 	u32 function;
 	u32 index;
@@ -48,6 +57,7 @@  static const struct cpuid_reg reverse_cpuid[] = {
 	[CPUID_7_1_EAX]       = {         7, 1, CPUID_EAX},
 	[CPUID_12_EAX]        = {0x00000012, 0, CPUID_EAX},
 	[CPUID_8000_001F_EAX] = {0x8000001f, 0, CPUID_EAX},
+	[CPUID_8000_0022_EAX] = {0x80000022, 0, CPUID_EAX},
 };
 
 /*