linux-kernel - Re: [PATCH 33/44] KVM: x86: Do VMX/SVM support checks directly in vendor code

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Message-ID: <6c71fcca-c17f-5979-e15e-afcf08899064@redhat.com>
Date:   Fri, 4 Nov 2022 09:02:32 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Marc Zyngier <maz@...nel.org>, Huacai Chen <chenhuacai@...nel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
        Anup Patel <anup@...infault.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Eric Farman <farman@...ux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Atish Patra <atishp@...shpatra.org>,
        David Hildenbrand <david@...hat.com>, kvm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        kvmarm@...ts.cs.columbia.edu, linux-mips@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Isaku Yamahata <isaku.yamahata@...el.com>,
        Fabiano Rosas <farosas@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Chao Gao <chao.gao@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yuan Yao <yuan.yao@...el.com>
Subject: Re: [PATCH 33/44] KVM: x86: Do VMX/SVM support checks directly in
 vendor code

On 11/3/22 19:58, Sean Christopherson wrote:
> 
> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> index 3e508f239098..ebe617ab0b37 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -191,6 +191,8 @@ static void default_init(struct cpuinfo_x86 *c)
>                          strcpy(c->x86_model_id, "386");
>          }
>   #endif
> +
> +       clear_cpu_cap(c, X86_FEATURE_MSR_IA32_FEAT_CTL);
>   }
>   
>   static const struct cpu_dev default_cpu = {

Not needed I think?  default_init does not call init_ia32_feat_ctl.

> diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
> index c881bcafba7d..3a7ae67f5a5e 100644
> --- a/arch/x86/kernel/cpu/cpuid-deps.c
> +++ b/arch/x86/kernel/cpu/cpuid-deps.c
> @@ -72,6 +72,8 @@ static const struct cpuid_dep cpuid_deps[] = {
>          { X86_FEATURE_AVX512_FP16,              X86_FEATURE_AVX512BW  },
>          { X86_FEATURE_ENQCMD,                   X86_FEATURE_XSAVES    },
>          { X86_FEATURE_PER_THREAD_MBA,           X86_FEATURE_MBA       },
> +       { X86_FEATURE_VMX,                      X86_FEATURE_MSR_IA32_FEAT_CTL         },
> +       { X86_FEATURE_SGX,                      X86_FEATURE_MSR_IA32_FEAT_CTL         },
>          { X86_FEATURE_SGX_LC,                   X86_FEATURE_SGX       },
>          { X86_FEATURE_SGX1,                     X86_FEATURE_SGX       },
>          { X86_FEATURE_SGX2,                     X86_FEATURE_SGX1      },
> 

Yes, good idea.

Paolo