linux-kernel - Re: [PATCH 06/20] x86/msr: Standardize on 'u32' MSR indices in <asm/msr.h>

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Message-ID: <e3d8db6a-dfb9-49d5-8c7f-b4a1d2faf575@zytor.com>
Date: Wed, 9 Apr 2025 23:14:12 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: Xin Li <xin@...or.com>, Ingo Molnar <mingo@...nel.org>,
        linux-kernel@...r.kernel.org
Cc: Juergen Gross <jgross@...e.com>, Dave Hansen <dave.hansen@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>, Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 06/20] x86/msr: Standardize on 'u32' MSR indices in
 <asm/msr.h>

On 4/9/25 20:53, Xin Li wrote:
> On 4/9/2025 8:29 PM, H. Peter Anvin wrote:
>> On April 9, 2025 8:18:12 PM PDT, Xin Li <xin@...or.com> wrote:
>>> A question NOT related to this patch set, the MSR write API prototype
>>> defined in struct pv_cpu_ops as:
>>>     void (*write_msr)(unsigned int msr, unsigned low, unsigned high);
>>>
>>> Will it be better to add "const" to its arguments?  I.e.,
>>>     void (*write_msr)(const u32 msr, const u32 low, const u32 high);
>>>
>>
>> No, that makes no sense (it would have absolutely no effect.)
>>
> 
> For the API definition, yes, it has no effect.
> 
> While it makes the API definition more explicit, and its implementations
> for native and Xen would be:
> 
> void {native,xen}_write_msr(const u32 msr, const u32 low, const u32 high)
> {
>      ....
> }
> 
> not worth it at all?
> 

No, and as you know, I'd like to get rid of the native_ and xen_ 
functions entirely anyway.

	-hpa