linux-kernel - Re: [PATCH v4 3/6] x86: KVM: Advertise AVX-IFMA CPUID to user space

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Date:   Mon, 21 Nov 2022 22:46:35 +0800
From:   Jiaxi Chen <jiaxi.chen@...ux.intel.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     kvm@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, pbonzini@...hat.com, ndesaulniers@...gle.com,
        alexandre.belloni@...tlin.com, peterz@...radead.org,
        jpoimboe@...nel.org, chang.seok.bae@...el.com,
        pawan.kumar.gupta@...ux.intel.com, babu.moger@....com,
        jmattson@...gle.com, sandipan.das@....com, tony.luck@...el.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, fenghua.yu@...el.com,
        keescook@...omium.org, nathan@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/6] x86: KVM: Advertise AVX-IFMA CPUID to user space



On 11/19/2022 12:08 AM, Sean Christopherson wrote:
> On Fri, Nov 18, 2022, Jiaxi Chen wrote:
>> AVX-IFMA is a new instruction in the latest Intel platform Sierra
>> Forest. This instruction packed multiplies unsigned 52-bit integers and
>> adds the low/high 52-bit products to Qword Accumulators.
>>
>> The bit definition:
>> CPUID.(EAX=7,ECX=1):EAX[bit 23]
>>
>> This CPUID is exposed to user space. Besides, there is no other VMX
>> control for this instruction.
>>
>> Signed-off-by: Jiaxi Chen <jiaxi.chen@...ux.intel.com>
>> ---
>>  arch/x86/include/asm/cpufeatures.h | 1 +
>>  arch/x86/kvm/cpuid.c               | 4 ++--
>>  2 files changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
>> index df4a7f7505a9..159f8b9898bf 100644
>> --- a/arch/x86/include/asm/cpufeatures.h
>> +++ b/arch/x86/include/asm/cpufeatures.h
>> @@ -310,6 +310,7 @@
>>  #define X86_FEATURE_AVX512_BF16		(12*32+ 5) /* AVX512 BFLOAT16 instructions */
>>  #define X86_FEATURE_CMPCCXADD           (12*32+ 7) /* CMPccXADD instructions */
>>  #define X86_FEATURE_AMX_FP16		(12*32+21) /* AMX fp16 Support */
>> +#define X86_FEATURE_AVX_IFMA            (12*32+23) /* Support for VPMADD52[H,L]UQ */
>>  
>>  /* AMD-defined CPU features, CPUID level 0x80000008 (EBX), word 13 */
>>  #define X86_FEATURE_CLZERO		(13*32+ 0) /* CLZERO instruction */
>> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
>> index 2a334d4cd04e..5726afb2d14c 100644
>> --- a/arch/x86/kvm/cpuid.c
>> +++ b/arch/x86/kvm/cpuid.c
>> @@ -657,8 +657,8 @@ void kvm_set_cpu_caps(void)
>>  		kvm_cpu_cap_set(X86_FEATURE_SPEC_CTRL_SSBD);
>>  
>>  	kvm_cpu_cap_mask(CPUID_7_1_EAX,
>> -		F(AVX_VNNI) | F(AVX512_BF16) | F(CMPCCXADD) | F(AMX_FP16)
>> -	);
>> +		F(AVX_VNNI) | F(AVX512_BF16) | F(CMPCCXADD) | F(AMX_FP16) |
>> +		F(AVX_IFMA));
> 
> Please keep the terminating paranthesis+semicolon on a separate line.  KVM isn't
> 100% consistent (as usual), but I would rather "fix" the cases that don't put
> the terminators on their own line. 

That's very careful. Thank you~
-- 
Regards,
Jiaxi