Re: [PATCH] x86: Prefer MWAIT over HALT on AMD processors

[Borislav Petkov <bp@alien8.de>]

On Tue, Apr 05, 2022 at 06:30:21PM +0530, Wyes Karny wrote:
> From: Lewis Caroll <lewis.carroll@amd.com>
> 
> Currently in the absence of the cpuidle driver (eg: when global
> C-States are disabled in the BIOS or when cpuidle is driver is not
> compiled in),

When does that ever happen?

Sounds like a very very niche situation to me...

> Here we enable MWAIT instruction as the default idle call for AMD
> Zen processors which support MWAIT. We retain the existing behaviour
> for older processors which depend on HALT.

Please use passive voice in your commit message: no "we" or "I", etc,
and describe your changes in imperative mood.

Also, pls read section "2) Describe your changes" in
Documentation/process/submitting-patches.rst for more details.

Also, see section "Changelog" in
Documentation/process/maintainer-tip.rst

Bottom line is: personal pronouns are ambiguous in text, especially with
so many parties/companies/etc developing the kernel so let's avoid them
please.

>  static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c)
>  {
> -	if (c->x86_vendor != X86_VENDOR_INTEL)
> +	if (!early_mwait_supported(c))

Isn't it enough to simply do here:

	if (cpu_has(c, X86_FEATURE_ZEN))
		return 1;

        if (c->x86_vendor != X86_VENDOR_INTEL)
                return 0;

	...


-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette