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From:   Jim Mattson <jmattson@google.com>
Date:   Tue, 4 May 2021 10:37:29 -0700
Message-ID: <CALMp9eToSSQ=8Dy4Vt5-GYEB4YB9c6-LTp8c60C97LOY9ufdjg@mail.gmail.com>
Subject: Re: [PATCH 01/15] KVM: VMX: Do not adverise RDPID if ENABLE_RDTSCP
 control is unsupported
To:     Sean Christopherson <seanjc@google.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Joerg Roedel <joro@8bytes.org>, kvm list <kvm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Xiaoyao Li <xiaoyao.li@intel.com>,
        Reiji Watanabe <reijiw@google.com>
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On Tue, May 4, 2021 at 10:17 AM Sean Christopherson <seanjc@google.com> wrote:
>
> Clear KVM's RDPID capability if the ENABLE_RDTSCP secondary exec control is
> unsupported.  Despite being enumerated in a separate CPUID flag, RDPID is
> bundled under the same VMCS control as RDTSCP and will #UD in VMX non-root
> if ENABLE_RDTSCP is not enabled.
>
> Fixes: 41cd02c6f7f6 ("kvm: x86: Expose RDPID in KVM_GET_SUPPORTED_CPUID")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sean Christopherson <seanjc@google.com>

But KVM will happily emulate RDPID if the instruction causes a #UD
VM-exit, won't it? See commit fb6d4d340e05 (KVM: x86: emulate RDPID).