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

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Message-ID: <0da43a86-81b0-4388-b47b-3a76b15f2a4c@citrix.com>
Date: Mon, 31 Mar 2025 22:45:43 +0100
From: Andrew Cooper <andrew.cooper3@...rix.com>
To: "Xin Li (Intel)" <xin@...or.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 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.

~Andrew