diff mbox series

[v3,2/6] KVM: x86: Introduce CPUID_8000_0007_EDX 'scattered' leaf

Message ID 20220916135205.3185973-3-vkuznets@redhat.com (mailing list archive)
State New, archived
Headers show
Series KVM: x86: Hyper-V invariant TSC control feature | expand

Commit Message

Vitaly Kuznetsov Sept. 16, 2022, 1:52 p.m. UTC 
CPUID_8000_0007_EDX may come handy when X86_FEATURE_CONSTANT_TSC
needs to be checked.

No functional change intended.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 arch/x86/kvm/cpuid.c         | 4 ++++
 arch/x86/kvm/reverse_cpuid.h | 9 ++++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

Comments

Sean Christopherson Sept. 20, 2022, 10:52 p.m. UTC | #1 
On Fri, Sep 16, 2022, Vitaly Kuznetsov wrote:
> CPUID_8000_0007_EDX may come handy when X86_FEATURE_CONSTANT_TSC
> needs to be checked.
> 
> No functional change intended.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  arch/x86/kvm/cpuid.c         | 4 ++++
>  arch/x86/kvm/reverse_cpuid.h | 9 ++++++++-
>  2 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 75dcf7a72605..f68b14053c9b 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -669,6 +669,10 @@ void kvm_set_cpu_caps(void)
>  	if (!tdp_enabled && IS_ENABLED(CONFIG_X86_64))
>  		kvm_cpu_cap_set(X86_FEATURE_GBPAGES);
>  
> +	kvm_cpu_cap_init_scattered(CPUID_8000_0007_EDX,
> +		SF(CONSTANT_TSC)
> +	);

The scattered leaf needs to be used in __do_cpuid_func(), e.g.

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index ffdc28684cb7..c91f23bb3605 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1137,8 +1137,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
                /* L2 cache and TLB: pass through host info. */
                break;
        case 0x80000007: /* Advanced power management */
-               /* invariant TSC is CPUID.80000007H:EDX[8] */
-               entry->edx &= (1 << 8);
+               cpuid_entry_override(entry, CPUID_8000_0007_EDX);
+
                /* mask against host */
                entry->edx &= boot_cpu_data.x86_power;
                entry->eax = entry->ebx = entry->ecx = 0;
Vitaly Kuznetsov Sept. 21, 2022, 8:17 a.m. UTC | #2 
Sean Christopherson <seanjc@google.com> writes:

> On Fri, Sep 16, 2022, Vitaly Kuznetsov wrote:
>> CPUID_8000_0007_EDX may come handy when X86_FEATURE_CONSTANT_TSC
>> needs to be checked.
>> 
>> No functional change intended.
>> 
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> ---
>>  arch/x86/kvm/cpuid.c         | 4 ++++
>>  arch/x86/kvm/reverse_cpuid.h | 9 ++++++++-
>>  2 files changed, 12 insertions(+), 1 deletion(-)
>> 
>> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
>> index 75dcf7a72605..f68b14053c9b 100644
>> --- a/arch/x86/kvm/cpuid.c
>> +++ b/arch/x86/kvm/cpuid.c
>> @@ -669,6 +669,10 @@ void kvm_set_cpu_caps(void)
>>  	if (!tdp_enabled && IS_ENABLED(CONFIG_X86_64))
>>  		kvm_cpu_cap_set(X86_FEATURE_GBPAGES);
>>  
>> +	kvm_cpu_cap_init_scattered(CPUID_8000_0007_EDX,
>> +		SF(CONSTANT_TSC)
>> +	);
>
> The scattered leaf needs to be used in __do_cpuid_func(), e.g.
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index ffdc28684cb7..c91f23bb3605 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -1137,8 +1137,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
>                 /* L2 cache and TLB: pass through host info. */
>                 break;
>         case 0x80000007: /* Advanced power management */
> -               /* invariant TSC is CPUID.80000007H:EDX[8] */
> -               entry->edx &= (1 << 8);
> +               cpuid_entry_override(entry, CPUID_8000_0007_EDX);
> +

Ah, missed that part! Will add.

>                 /* mask against host */
>                 entry->edx &= boot_cpu_data.x86_power;
>                 entry->eax = entry->ebx = entry->ecx = 0;
>
diff mbox series

Patch

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 75dcf7a72605..f68b14053c9b 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -669,6 +669,10 @@  void kvm_set_cpu_caps(void)
 	if (!tdp_enabled && IS_ENABLED(CONFIG_X86_64))
 		kvm_cpu_cap_set(X86_FEATURE_GBPAGES);
 
+	kvm_cpu_cap_init_scattered(CPUID_8000_0007_EDX,
+		SF(CONSTANT_TSC)
+	);
+
 	kvm_cpu_cap_mask(CPUID_8000_0008_EBX,
 		F(CLZERO) | F(XSAVEERPTR) |
 		F(WBNOINVD) | F(AMD_IBPB) | F(AMD_IBRS) | F(AMD_SSBD) | F(VIRT_SSBD) |
diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
index a19d473d0184..a5514c89dc29 100644
--- a/arch/x86/kvm/reverse_cpuid.h
+++ b/arch/x86/kvm/reverse_cpuid.h
@@ -12,7 +12,8 @@ 
  * "bug" caps, but KVM doesn't use those.
  */
 enum kvm_only_cpuid_leafs {
-	CPUID_12_EAX	 = NCAPINTS,
+	CPUID_12_EAX		= NCAPINTS,
+	CPUID_8000_0007_EDX	= NCAPINTS + 1,
 	NR_KVM_CPU_CAPS,
 
 	NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
@@ -24,6 +25,9 @@  enum kvm_only_cpuid_leafs {
 #define KVM_X86_FEATURE_SGX1		KVM_X86_FEATURE(CPUID_12_EAX, 0)
 #define KVM_X86_FEATURE_SGX2		KVM_X86_FEATURE(CPUID_12_EAX, 1)
 
+/* CPUID level 0x80000007 (EDX). */
+#define KVM_X86_FEATURE_CONSTANT_TSC	KVM_X86_FEATURE(CPUID_8000_0007_EDX, 8)
+
 struct cpuid_reg {
 	u32 function;
 	u32 index;
@@ -48,6 +52,7 @@  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_0007_EDX] = {0x80000007, 0, CPUID_EDX},
 };
 
 /*
@@ -78,6 +83,8 @@  static __always_inline u32 __feature_translate(int x86_feature)
 		return KVM_X86_FEATURE_SGX1;
 	else if (x86_feature == X86_FEATURE_SGX2)
 		return KVM_X86_FEATURE_SGX2;
+	else if (x86_feature == X86_FEATURE_CONSTANT_TSC)
+		return KVM_X86_FEATURE_CONSTANT_TSC;
 
 	return x86_feature;
 }