linux-kernel - Re: [PATCH v1 2/3] x86/msr: Switch between WRMSRNS and WRMSR with the alternatives mechanism

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Message-ID: <b5221fb0-a198-4c76-ae47-906c42442f5c@zytor.com>
Date: Sat, 17 Aug 2024 23:16:36 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: Borislav Petkov <bp@...en8.de>
Cc: Xin Li <xin@...or.com>, Andrew Cooper <andrew.cooper3@...rix.com>,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        dave.hansen@...ux.intel.com, x86@...nel.org, peterz@...radead.org,
        seanjc@...gle.com
Subject: Re: [PATCH v1 2/3] x86/msr: Switch between WRMSRNS and WRMSR with the
 alternatives mechanism

On 8/17/24 22:49, Borislav Petkov wrote:
> On Sat, Aug 17, 2024 at 12:22:22PM -0700, H. Peter Anvin wrote:
>> The padding avoids unnecessary NOPs.
> 
> And a NOP vs some other prefix to have one less insn matters practically
> how exactly here?

Pretty much nothing, but it is zero cost and possibly some insanely 
small gain.

	-hpa