From: Paolo Bonzini <pbonzini@redhat.com>
To: Borislav Petkov <bp@alien8.de>, "Luc, Piotr" <Piotr.Luc@intel.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"he.chen@linux.intel.com" <he.chen@linux.intel.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"x86@kernel.org" <x86@kernel.org>,
"hpa@zytor.com" <hpa@zytor.com>,
"mingo@redhat.com" <mingo@redhat.com>,
"Kang, Luwei" <luwei.kang@intel.com>,
"rkrcmar@redhat.com" <rkrcmar@redhat.com>
Subject: Re: [PATCH] x86/cpuid: expose AVX512_4VNNIW and AVX512_4FMAPS features to kvm guest
Date: Mon, 31 Oct 2016 11:47:48 +0100 [thread overview]
Message-ID: <48ef617f-c438-cfcf-6f0c-1eb3b59820ff@redhat.com> (raw)
In-Reply-To: <20161031103050.k7b2l64blhmv33mw@pd.tnic>
On 31/10/2016 11:30, Borislav Petkov wrote:
> On Mon, Oct 31, 2016 at 10:18:41AM +0000, Luc, Piotr wrote:
>> The cpuid_mask function, which usually used in kvm, read bit from this
>> x86_capabity and mask out. This prevents passing disabled features to
>> guest. If we use cpu_count instead, which reports bits directly from
>
> Ah, you mean cpuid_count().
>
>> CPU, then the bits of features that are disabled in host are passed to
>> guest as enabled. This seems be inconsistent.
>
> Ok, I see what you mean.
>
> So I guess we'll have to iterate over the cpuid_bits[] array and
> recreate the CPUID leaf for KVM instead, as I suggested earlier.
Yes, indeed. :(
The information is all in arch/x86/kernel/cpu/scattered.c's cpuid_bits
array. Borislav, would it be okay to export the cpuid_regs enum?
Paolo
next prev parent reply other threads:[~2016-10-31 10:47 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
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 [this message]
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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