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[34.168.104.7]) by smtp.gmail.com with ESMTPSA id z4-20020a1709027e8400b0017da2798025sm914686pla.295.2022.11.03.11.35.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Nov 2022 11:35:08 -0700 (PDT) Date: Thu, 3 Nov 2022 18:35:05 +0000 From: Sean Christopherson To: Paolo Bonzini Cc: Marc Zyngier , Huacai Chen , Aleksandar Markovic , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Matthew Rosato , Eric Farman , Vitaly Kuznetsov , James Morse , Alexandru Elisei , Suzuki K Poulose , Oliver Upton , Atish Patra , David Hildenbrand , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Isaku Yamahata , Fabiano Rosas , Michael Ellerman , Chao Gao , Thomas Gleixner , Yuan Yao Subject: Re: [PATCH 33/44] KVM: x86: Do VMX/SVM support checks directly in vendor code Message-ID: References: <20221102231911.3107438-1-seanjc@google.com> <20221102231911.3107438-34-seanjc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On Thu, Nov 03, 2022, Paolo Bonzini wrote: > On 11/3/22 00:19, Sean Christopherson wrote: > > + if (!boot_cpu_has(X86_FEATURE_MSR_IA32_FEAT_CTL) || > > + !boot_cpu_has(X86_FEATURE_VMX)) { > > + pr_err("VMX not enabled in MSR_IA32_FEAT_CTL\n"); > > + return false; > > I think the reference to the BIOS should remain in these messages and in > svm.c (even though these days it's much less common for vendors to default > to disabled virtualization in the system setup). Ya, I'll figure out a way to mention BIOS/firmware. > The check for X86_FEATURE_MSR_IA32_FEAT_CTL is not needed because > init_ia32_feat_ctl() will clear X86_FEATURE_VMX if the rdmsr fail (and not > set X86_FEATURE_MSR_IA32_FEAT_CTL). It's technically required. IA32_FEAT_CTL and thus KVM_INTEL depends on any of CPU_SUP_{INTEL,CENATUR,ZHAOXIN}, but init_ia32_feat_ctl() is invoked if and only if the actual CPU type matches one of the aforementioned CPU_SUP_*. E.g. running a kernel built with CONFIG_CPU_SUP_INTEL=y CONFIG_CPU_SUP_AMD=y # CONFIG_CPU_SUP_HYGON is not set # CONFIG_CPU_SUP_CENTAUR is not set # CONFIG_CPU_SUP_ZHAOXIN is not set on a Cenatur or Zhaoxin CPU will leave X86_FEATURE_VMX set but not set X86_FEATURE_MSR_IA32_FEAT_CTL. If VMX isn't enabled in MSR_IA32_FEAT_CTL, KVM will get unexpected #UDs when trying to enable VMX.