linux-kernel - Re: [RFC PATCH v1 01/15] x86/msr: Replace __wrmsr() with native

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Message-ID: <9618fccf-3620-4395-bdac-aa8999fe2437@zytor.com>
Date: Thu, 3 Apr 2025 00:13:35 -0700
From: Xin Li <xin@...or.com>
To: Andrew Cooper <andrew.cooper3@...rix.com>, linux-kernel@...r.kernel.org,
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Subject: Re: [RFC PATCH v1 01/15] x86/msr: Replace __wrmsr() with
 native_wrmsrl()

On 3/31/2025 2:45 PM, Andrew Cooper wrote:
> On 31/03/2025 9:22 am, Xin Li (Intel) wrote:
>> __wrmsr() is the lowest level primitive MSR write API, and its direct
>> use is NOT preferred.  Use its wrapper function native_wrmsrl() instead.
>>
>> No functional change intended.
>>
>> Signed-off-by: Xin Li (Intel) <xin@...or.com>
> 
> The critical piece of information you're missing from the commit message
> is that the MSR_IMM instructions take a single u64.
> 
> Therefore to use them, you've got to arrange for all callers to provide
> a single u64, rather than a split u32 pair.

You definitely caught me on how I was thinking it ;)

Sometimes it is nice to see a change log with a thinking process.

Thanks!
     Xin