Messages in this thread | | | Subject | Re: [PATCH v3 2/3] x86: Remove vendor checks from prefer_mwait_c1_over_halt | From | Zhang Rui <> | Date | Wed, 25 May 2022 15:20:48 +0800 |
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Hi, Wyes,
On Mon, 2022-05-23 at 21:19 +0530, Wyes Karny wrote: > Hello Rui, > > On 5/20/2022 7:13 PM, Zhang Rui wrote: > > On Thu, 2022-05-19 at 09:00 -0700, Dave Hansen wrote: > > > On 5/10/22 03:18, Wyes Karny wrote: > > > > static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 > > > > *c) > > > > { > > > > + u32 eax, ebx, ecx, edx; > > > > + > > > > /* User has disallowed the use of MWAIT. Fallback to > > > > HALT */ > > > > if (boot_option_idle_override == IDLE_NOMWAIT) > > > > return 0; > > > > > > > > - if (c->x86_vendor != X86_VENDOR_INTEL) > > > > + /* MWAIT is not supported on this platform. Fallback to > > > > HALT */ > > > > + if (!cpu_has(c, X86_FEATURE_MWAIT)) > > > > return 0; > > > > I'm new to x86 code, a dumb question, what about the other vendors? > > with this patch, prefer_mwait_c1_over_halt() can return 1 for other > > vendors as well? > > This decision tree is based on cpuid features, so if the processor > advertises MWAIT C1 support we would be choosing MWAIT. > If any vendor wants to avoid choosing MWAIT (even cpuid shows MWAIT > C1 > support), they can explicitly mention. Will add exceptions form them. > That's my concern.
This patch indeed changes the behaviors for vendors other than Intel and AMD. I don't know the impact of this, but just point out a behavior change caused by this patch.
thanks, rui
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