linux-kernel - Re: [PATCH v1 2/4] x86/fred: Write to FRED MSRs with wrmsrns()

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Message-ID: <9063b0fe-e8f3-44ff-b323-b2b6c338690f@intel.com>
Date: Wed, 3 Jul 2024 08:43:46 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: "Xin Li (Intel)" <xin@...or.com>, linux-kernel@...r.kernel.org
Cc: hpa@...or.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, x86@...nel.org, peterz@...radead.org,
 andrew.cooper3@...rix.com, nik.borisov@...e.com, houwenlong.hwl@...group.com
Subject: Re: [PATCH v1 2/4] x86/fred: Write to FRED MSRs with wrmsrns()

On 7/3/24 01:54, Xin Li (Intel) wrote:
> Do FRED MSR writes with wrmsrns() rather than wrmsrl().

A longer changelog would be appreciated here.  The wrmsrns() is
presumably to avoid the WRMSR serialization overhead and the CR4 write
provides all of the serialization that we need.

I'm also not clear how this fits into the series other than being FRED
related.

> No functional change intended.

I think I know what this was trying to convey, but I'm not sure this
phrase is appropriate to use here.  Sure, WRMSR and WRMSRNS have the
same general purpose, but I'd never say they are functionally equivalent.