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SubjectRe: [PATCH] x86/cstate: Replace vendor check with X86_FEATURE_MWAIT in ffh_cstate_init
On Fri, Jul 1, 2022 at 9:05 AM Tony W Wang-oc <TonyWWang-oc@zhaoxin.com> 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@zhaoxin.com>

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

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


> ---
> 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
>

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