linux-kernel - Re: [PATCH 1/2] KVM: x86: Advertise CPUID.(EAX=7,ECX=2):EDX[5:0] to userspace

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Message-ID: <170137622057.658898.161602473001495929.b4-ty@google.com>
Date:   Thu, 30 Nov 2023 17:52:10 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "'Paolo Bonzini '" <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH 1/2] KVM: x86: Advertise CPUID.(EAX=7,ECX=2):EDX[5:0] to userspace

On Mon, 23 Oct 2023 17:16:35 -0700, Jim Mattson wrote:
> The low five bits {INTEL_PSFD, IPRED_CTRL, RRSBA_CTRL, DDPD_U, BHI_CTRL}
> advertise the availability of specific bits in IA32_SPEC_CTRL. Since KVM
> dynamically determines the legal IA32_SPEC_CTRL bits for the underlying
> hardware, the hard work has already been done. Just let userspace know
> that a guest can use these IA32_SPEC_CTRL bits.
> 
> The sixth bit (MCDT_NO) states that the processor does not exhibit MXCSR
> Configuration Dependent Timing (MCDT) behavior. This is an inherent
> property of the physical processor that is inherited by the virtual
> CPU. Pass that information on to userspace.
> 
> [...]

Applied to kvm-x86 misc, with macros to make Jim queasy (but they really do
guard against copy+paste errors).

[1/2] KVM: x86: Advertise CPUID.(EAX=7,ECX=2):EDX[5:0] to userspace
      https://github.com/kvm-x86/linux/commit/eefe5e668209
[2/2] KVM: x86: Use a switch statement and macros in __feature_translate()
      https://github.com/kvm-x86/linux/commit/80c883db87d9

--
https://github.com/kvm-x86/linux/tree/next