Re: [PATCH] x86/cstate: Replace vendor check with X86_FEATURE_MWAIT in ffh_cstate_init

[Tony W Wang-oc]

On 2022/7/6 上午2:45, Rafael J. Wysocki wrote:
> On Fri, Jul 1, 2022 at 9:05 AM Tony W Wang-oc <TonyWWang-oc@xxxxxxxxxxx> wrote:
> > The original commit 991528d73486 ("ACPI: Processor native C-states using
> > MWAIT") has a vendor check for Intel in the function of ffh_cstate_init().
> >
> > Commit 5209654a46ee ("x86/ACPI/cstate: Allow ACPI C1 FFH MWAIT use on AMD
> > systems") and commit 280b68a3b3b9 ("x86/cstate: Allow ACPI C1 FFH MWAIT
> > use on Hygon systems") add vendor check for AMD and HYGON in the function
> > of ffh_cstate_init().
> >
> > Recent Zhaoxin and Centaur CPUs support MONITOR/MWAIT instructions that
> > can be used for ACPI Cx state in the same way as Intel. So expected to
> > add the support of these CPUs in the function of ffh_cstate_init() too.
> >
> > The CPU feature X86_FEATURE_MWAIT indicates processor supports MONITOR/
> > MWAIT instructions. So the check for many CPU vendors in ffh_cstate_init()
> > is unnecessary, use X86_FEATURE_MWAIT to replace the CPU vendor check.
> >
> > Signed-off-by: Tony W Wang-oc <TonyWWang-oc@xxxxxxxxxxx>
>
> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

Thanks a lot.
Add some original commit authors this patch related to.

> or please let me know if I'm expected to pick up this one.  Thanks!

Yes for me. Thanks a lot.

> > ---
> >   arch/x86/kernel/acpi/cstate.c | 6 +-----
> >   1 file changed, 1 insertion(+), 5 deletions(-)
> >
> > diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
> > index 7945eae..a64c38f 100644
> > --- a/arch/x86/kernel/acpi/cstate.c
> > +++ b/arch/x86/kernel/acpi/cstate.c
> > @@ -209,11 +209,7 @@ EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_enter);
> >
> >   static int __init ffh_cstate_init(void)
> >   {
> > -       struct cpuinfo_x86 *c = &boot_cpu_data;
> > -
> > -       if (c->x86_vendor != X86_VENDOR_INTEL &&
> > -           c->x86_vendor != X86_VENDOR_AMD &&
> > -           c->x86_vendor != X86_VENDOR_HYGON)
> > +       if (!boot_cpu_has(X86_FEATURE_MWAIT))
> >                  return -1;
> >
> >          cpu_cstate_entry = alloc_percpu(struct cstate_entry);
> > --
> > 2.7.4
> .