linux-kernel - Re: [PATCH 3/6] x86/msr: minimize usage of native

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Message-ID: <aBobn8kaiDVCEqK4@google.com>
Date: Tue, 6 May 2025 07:24:31 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Juergen Gross <jgross@...e.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org, linux-hyperv@...r.kernel.org, 
	kvm@...r.kernel.org, xin@...or.com, "K. Y. Srinivasan" <kys@...rosoft.com>, 
	Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, 
	Dexuan Cui <decui@...rosoft.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, 
	"H. Peter Anvin" <hpa@...or.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Vitaly Kuznetsov <vkuznets@...hat.com>, Boris Ostrovsky <boris.ostrovsky@...cle.com>, 
	xen-devel@...ts.xenproject.org
Subject: Re: [PATCH 3/6] x86/msr: minimize usage of native_*() msr access functions

On Tue, May 06, 2025, Juergen Gross wrote:
> In order to prepare for some MSR access function reorg work, switch
> most users of native_{read|write}_msr[_safe]() to the more generic
> rdmsr*()/wrmsr*() variants.
> 
> For now this will have some intermediate performance impact with
> paravirtualization configured when running on bare metal, but this
> is a prereq change for the planned direct inlining of the rdmsr/wrmsr
> instructions with this configuration.

Oh the horror, KVM's probing of errata will be marginally slower :-)

> The main reason for this switch is the planned move of the MSR trace
> function invocation from the native_*() functions to the generic
> rdmsr*()/wrmsr*() variants. Without this switch the users of the
> native_*() functions would lose the related tracing entries.
> 
> Note that the Xen related MSR access functions will not be switched,
> as these will be handled after the move of the trace hooks.
> 
> Signed-off-by: Juergen Gross <jgross@...e.com>
> ---

Acked-by: Sean Christopherson <seanjc@...gle.com>