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Subject: Re: [PATCH] x86/cstate: Replace vendor check with X86_FEATURE_MWAIT
 in ffh_cstate_init
To:     "Rafael J. Wysocki" <rafael@kernel.org>
CC:     Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
        "Thomas Gleixner" <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "Borislav Petkov" <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Linux PM <linux-pm@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        <CobeChen@zhaoxin.com>, <TimGuo@zhaoxin.com>,
        <LindaChai@zhaoxin.com>, <LeoLiu@zhaoxin.com>,
        <venkatesh.pallipadi@intel.com>, <yazen.ghannam@amd.com>,
        <puwen@hygon.cn>
References: <1656659147-20396-1-git-send-email-TonyWWang-oc@zhaoxin.com>
 <CAJZ5v0jXZKECfaJ0fqx+Hb5vhaw6uFgOaJD1BxwRUjOfMXMJJQ@mail.gmail.com>
From:   Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
Message-ID: <993cf518-0ec6-639d-039a-6a2a1b1b5793@zhaoxin.com>
Date:   Tue, 19 Jul 2022 11:36:01 +0800
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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@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>
> 

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
>>
> .
>