linux-kernel - Re: [PATCH] x86/cpuid: expose AVX512_4VNNIW and AVX512

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Message-ID: <20161029122548.niyvh2q3kuvyqwo3@pd.tnic>
Date:   Sat, 29 Oct 2016 14:25:48 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Piotr Luc <Piotr.Luc@...el.com>, kvm@...r.kernel.org,
        he chen <he.chen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, x86@...nel.org,
        hpa@...or.com, mingo@...hat.com, Luwei Kang <luwei.kang@...el.com>,
        rkrcmar@...hat.com
Subject: Re: [PATCH] x86/cpuid: expose AVX512_4VNNIW and AVX512_4FMAPS
 features to kvm guest

On Sat, Oct 29, 2016 at 08:21:17AM -0400, Paolo Bonzini wrote:
> Currently none of the bits in CPUID[7,0].edx is ever masked by the host, so
> this would be enough.  If we ever need to do some masking, I guess I'll
> practice my puss-in-boots look and submit a patch to add CPUID[7,0] back
> as a separate cpufeature entr.

I don't understand - why can't it be filtered here if needed? I.e.,

	return edx & KVM_CPUID_EDX_7_MASK;

or so?

Btw, we already have a cpuid_edx() helper in arch/x86/include/asm/processor.h

-- 
Regards/Gruss,
    Boris.

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