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

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Message-ID: <20161028122123.24i3synevehn6r3p@pd.tnic>
Date:   Fri, 28 Oct 2016 14:21:23 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     "Luc, Piotr" <Piotr.Luc@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "he.chen@...ux.intel.com" <he.chen@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "Kang, Luwei" <luwei.kang@...el.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>
Subject: Re: [PATCH] x86/cpuid: expose AVX512_4VNNIW and AVX512_4FMAPS
 features to kvm guest

On Fri, Oct 28, 2016 at 02:07:21PM +0200, Paolo Bonzini wrote:
> cpuid_count_edx would be just
> 
> static inline unsigned int cpuid_count_edx(unsigned op, unsigned count)
> {
>         unsigned int eax, ebx, ecx, edx;
> 
>         cpuid_count(op, count, &eax, &ebx, &ecx, &edx);
> 
>         return edx;
> }

Even better.

But shouldn't this be hiding unimplemented CPUID bits from the guest?

-- 
Regards/Gruss,
    Boris.

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