linux-kernel - Re: [RFC PATCH v1 10/15] KVM: VMX: Use WRMSRNS or its immediate form when available

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Message-ID: <0cad1e0b-2bfd-4258-90cd-8d319bf0e74a@zytor.com>
Date: Mon, 14 Apr 2025 10:48:47 -0700
From: Xin Li <xin@...or.com>
To: "H. Peter Anvin" <hpa@...or.com>, Jim Mattson <jmattson@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        linux-hyperv@...r.kernel.org, virtualization@...ts.linux.dev,
        linux-edac@...r.kernel.org, kvm@...r.kernel.org,
        xen-devel@...ts.xenproject.org, linux-ide@...r.kernel.org,
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Subject: Re: [RFC PATCH v1 10/15] KVM: VMX: Use WRMSRNS or its immediate form
 when available

On 4/12/2025 4:10 PM, H. Peter Anvin wrote:
> Also,*in this specific case* IA32_SPEC_CTRL is architecturally nonserializing, i.e. WRMSR executes as WRMSRNS anyway.

While the immediate form WRMSRNS could be faster because the MSR index
is available *much* earlier in the pipeline, right?