From: Paolo Bonzini <pbonzini@redhat.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Piotr Luc <Piotr.Luc@intel.com>,
kvm@vger.kernel.org, he chen <he.chen@linux.intel.com>,
linux-kernel@vger.kernel.org, tglx@linutronix.de, x86@kernel.org,
hpa@zytor.com, mingo@redhat.com,
Luwei Kang <luwei.kang@intel.com>,
rkrcmar@redhat.com
Subject: Re: [PATCH] x86/cpuid: expose AVX512_4VNNIW and AVX512_4FMAPS features to kvm guest
Date: Sat, 29 Oct 2016 08:21:17 -0400 (EDT) [thread overview]
Message-ID: <425702906.9319122.1477743677017.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <20161028122123.24i3synevehn6r3p@pd.tnic>
----- Original Message -----
> From: "Borislav Petkov" <bp@alien8.de>
> To: "Paolo Bonzini" <pbonzini@redhat.com>
> Cc: "Piotr Luc" <Piotr.Luc@intel.com>, kvm@vger.kernel.org, "he chen" <he.chen@linux.intel.com>,
> linux-kernel@vger.kernel.org, tglx@linutronix.de, x86@kernel.org, hpa@zytor.com, mingo@redhat.com, "Luwei Kang"
> <luwei.kang@intel.com>, rkrcmar@redhat.com
> Sent: Friday, October 28, 2016 2:21:23 PM
> 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?
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.
Paolo
next prev parent reply other threads:[~2016-10-29 12:22 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-28 9:12 [PATCH] x86/cpuid: expose AVX512_4VNNIW and AVX512_4FMAPS features to kvm guest He Chen
2016-10-28 9:31 ` Paolo Bonzini
2016-10-28 9:46 ` He Chen
2016-10-28 9:54 ` Paolo Bonzini
2016-10-28 9:55 ` He Chen
2016-10-28 10:13 ` Luc, Piotr
2016-10-28 10:17 ` Paolo Bonzini
2016-10-28 11:08 ` Borislav Petkov
2016-10-28 12:07 ` Paolo Bonzini
2016-10-28 12:21 ` Borislav Petkov
2016-10-29 12:21 ` Paolo Bonzini [this message]
2016-10-29 12:25 ` Borislav Petkov
2016-10-29 12:36 ` Paolo Bonzini
2016-10-29 12:53 ` Borislav Petkov
2016-10-29 13:20 ` Paolo Bonzini
2016-10-31 9:15 ` Luc, Piotr
2016-10-31 9:53 ` Borislav Petkov
2016-10-31 10:18 ` Luc, Piotr
2016-10-31 10:30 ` Borislav Petkov
2016-10-31 10:47 ` Paolo Bonzini
2016-10-31 11:05 ` Borislav Petkov
2016-10-31 11:41 ` Paolo Bonzini
2016-11-01 7:48 ` He Chen
2016-11-01 8:46 ` Borislav Petkov
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