2022-09-16 14:14:49

by Vitaly Kuznetsov

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

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 <[email protected]>
---
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)
+ );
+
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;
}
--
2.37.2

2022-09-20 23:24:55

by Sean Christopherson

Subject: Re: [PATCH v3 2/6] KVM: x86: Introduce CPUID_8000_0007_EDX 'scattered' leaf

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 <[email protected]>
> ---
> 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;

2022-09-21 08:23:56

by Vitaly Kuznetsov

Subject: Re: [PATCH v3 2/6] KVM: x86: Introduce CPUID_8000_0007_EDX 'scattered' leaf

Sean Christopherson <[email protected]> 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 <[email protected]>
>> ---
>> 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;
>

--
Vitaly