linux-kernel - Re: [PATCH 3/5] KVM: x86: Apply TSX_CTRL_CPUID_CLEAR if and only if the vCPU has RTM or HLE

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Message-ID: <CALMp9eQjGXrCpuwqYc5sddrTNWRO+gA-P0jONtzfb8W-E2STBw@mail.gmail.com>
Date: Fri, 13 Dec 2024 06:39:51 -0800
From: Jim Mattson <jmattson@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] KVM: x86: Apply TSX_CTRL_CPUID_CLEAR if and only if
 the vCPU has RTM or HLE

On Tue, Dec 10, 2024 at 5:33 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> When emulating CPUID, retrieve MSR_IA32_TSX_CTRL.TSX_CTRL_CPUID_CLEAR if
> and only if RTM and/or HLE feature bits need to be cleared.  Getting the
> MSR value is unnecessary if neither bit is set, and avoiding the lookup
> saves ~80 cycles for vCPUs without RTM or HLE.
>
> Cc: Jim Mattson <jmattson@...gle.com>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

I'm not sure why you cc'd me :), but...

Reviewed-by: Jim Mattson <jmattson@...gle.com>