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([2001:b07:add:ec09:c399:bc87:7b6c:fb2a]) by smtp.googlemail.com with ESMTPSA id qk4-20020a170906d9c400b007ad69e9d34dsm5756143ejb.54.2022.11.02.11.16.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Nov 2022 11:16:38 -0700 (PDT) Message-ID: Date: Wed, 2 Nov 2022 19:16:37 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.0 Subject: Re: [PATCH 2/6] x86: KVM: Enable AMX-FP16 CPUID and expose it to guest Content-Language: en-US To: Dave Hansen , Jiaxi Chen , 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 References: <20221019084734.3590760-1-jiaxi.chen@linux.intel.com> <20221019084734.3590760-3-jiaxi.chen@linux.intel.com> <639c22a1-b0b0-9fb0-2a9a-060c53f9f540@intel.com> From: Paolo Bonzini In-Reply-To: <639c22a1-b0b0-9fb0-2a9a-060c53f9f540@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Paolo