From: Dave Hansen <dave.hansen@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
Jiaxi Chen <jiaxi.chen@linux.intel.com>,
kvm@vger.kernel.org
Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com,
seanjc@google.com, ndesaulniers@google.com,
alexandre.belloni@bootlin.com, peterz@infradead.org,
jpoimboe@kernel.org, chang.seok.bae@intel.com,
pawan.kumar.gupta@linux.intel.com, babu.moger@amd.com,
jmattson@google.com, sandipan.das@amd.com, tony.luck@intel.com,
sathyanarayanan.kuppuswamy@linux.intel.com, fenghua.yu@intel.com,
keescook@chromium.org, jane.malalane@citrix.com,
nathan@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/6] x86: KVM: Enable AMX-FP16 CPUID and expose it to guest
Date: Wed, 2 Nov 2022 11:21:52 -0700 [thread overview]
Message-ID: <c00a4715-94f7-2d4a-02b3-533bb309c130@intel.com> (raw)
In-Reply-To: <aa7f6efc-de4c-c5f6-fb5f-ef514e4513a3@redhat.com>
On 11/2/22 11:16, Paolo Bonzini wrote:
> On 11/2/22 19:14, Dave Hansen wrote:
>>> kvm_cpu_cap_mask(CPUID_7_1_EAX,
>>> - F(AVX_VNNI) | F(AVX512_BF16) | F(CMPCCXADD)
>>> + F(AVX_VNNI) | F(AVX512_BF16) | F(CMPCCXADD) | F(AMX_FP16)
>>> );
>>> kvm_cpu_cap_mask(CPUID_D_1_EAX,
>>
>> KVM folks, is the idea that every feature that is enumerated to a guest
>> needs to be in one of these masks? Or is there something special about
>> the features in these masks?
>
> Yes, all features are vetted manually to see whether they require new
> MSRs and the like. Therefore, anything that userspace can set in the
> guest's CPUID must be in the list.
Makes sense.
Intel folks, when you add these bits, can you please include information
about the "vetting" that you performed?
For example, it would be handy to say:
AMX_FP16 is just a new instruction that operates on existing AMX
tile registers. It needs no additional enabling on top of the
existing kernel AMX enabling.
next prev parent reply other threads:[~2022-11-02 18:23 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-19 8:47 [PATCH 0/6] x86: KVM: Expose CPUID to guest for new Intel platform instructions Jiaxi Chen
2022-10-19 8:47 ` [PATCH 1/6] x86: KVM: Enable CMPccXADD CPUID and expose it to guest Jiaxi Chen
2022-10-19 15:15 ` Sean Christopherson
2022-10-20 7:27 ` Chen, Jiaxi
2022-10-26 3:40 ` Jiaxi Chen
2022-10-26 17:15 ` Borislav Petkov
2022-10-27 2:27 ` Jiaxi Chen
2022-11-01 9:07 ` Jiaxi Chen
2022-11-01 15:07 ` Sean Christopherson
2022-11-03 2:35 ` Jiaxi Chen
2022-10-19 8:47 ` [PATCH 2/6] x86: KVM: Enable AMX-FP16 " Jiaxi Chen
2022-11-02 18:14 ` Dave Hansen
2022-11-02 18:16 ` Paolo Bonzini
2022-11-02 18:21 ` Dave Hansen [this message]
2022-11-03 2:38 ` Jiaxi Chen
2022-10-19 8:47 ` [PATCH 3/6] x86: KVM: Enable AVX-IFMA " Jiaxi Chen
2022-10-19 8:47 ` [PATCH 4/6] x86: KVM: Enable AVX-VNNI-INT8 " Jiaxi Chen
2022-10-19 8:52 ` Borislav Petkov
2022-10-19 14:57 ` Sean Christopherson
2022-10-19 15:09 ` Sean Christopherson
2022-10-26 3:33 ` Jiaxi Chen
2022-10-20 7:13 ` Chen, Jiaxi
2022-10-19 8:47 ` [PATCH 5/6] x86: KVM: Enable AVX-NE-CONVERT " Jiaxi Chen
2022-10-19 8:47 ` [PATCH 6/6] x86: KVM: Enable PREFETCHIT0/1 " Jiaxi Chen
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