linux-kernel - Re: [PATCH 1/4 v3] x86: AMD: Replace numeric value for SME CPUID leaf with a #define

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Message-ID: <c11dee69-e5fe-ce7a-8912-17393d2e1452@redhat.com>
Date:   Sat, 12 Sep 2020 08:54:27 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Borislav Petkov <bp@...en8.de>,
        Krish Sadhukhan <krish.sadhukhan@...cle.com>
Cc:     kvm@...r.kernel.org, jmattson@...gle.com, tglx@...utronix.de,
        mingo@...hat.com, x86@...nel.org, sean.j.christopherson@...el.com,
        vkuznets@...hat.com, wanpengli@...cent.com, joro@...tes.org,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        linux-kernel@...r.kernel.org, hpa@...or.com
Subject: Re: [PATCH 1/4 v3] x86: AMD: Replace numeric value for SME CPUID leaf
 with a #define

On 11/09/20 23:21, Borislav Petkov wrote:
> On Fri, Sep 11, 2020 at 07:25:58PM +0000, Krish Sadhukhan wrote:
> 
> <-- patches need commit message.
> 
> ...
> 
>> diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
>> index 62b137c3c97a..033c112e03fc 100644
>> --- a/arch/x86/kernel/cpu/scattered.c
>> +++ b/arch/x86/kernel/cpu/scattered.c
>> @@ -39,8 +39,8 @@ static const struct cpuid_bit cpuid_bits[] = {
>>  	{ X86_FEATURE_CPB,		CPUID_EDX,  9, 0x80000007, 0 },
>>  	{ X86_FEATURE_PROC_FEEDBACK,    CPUID_EDX, 11, 0x80000007, 0 },
>>  	{ X86_FEATURE_MBA,		CPUID_EBX,  6, 0x80000008, 0 },
>> -	{ X86_FEATURE_SME,		CPUID_EAX,  0, 0x8000001f, 0 },
>> -	{ X86_FEATURE_SEV,		CPUID_EAX,  1, 0x8000001f, 0 },
>> +	{ X86_FEATURE_SME,		CPUID_EAX,  0, CPUID_AMD_SME, 0 },
>> +	{ X86_FEATURE_SEV,		CPUID_EAX,  1, CPUID_AMD_SME, 0 },
> 
> So this one gets a name and all the others above don't?
> 
> This fact should've given you a hint that there's no need for naming
> CPUID leafs - it is easier to grep CPU manuals by the values so you can
> drop this patch.

Also, there'd be confusion between the CPUID_* enum in
arch/x86/include/asm/cpufeature.h.

Paolo