linux-kernel - [PATCH] x86/cstate: Replace vendor check with X86_FEATURE_MWAIT in ffh_cstate

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Message-ID: <1656659147-20396-1-git-send-email-TonyWWang-oc@zhaoxin.com>
Date:   Fri, 1 Jul 2022 15:05:47 +0800
From:   Tony W Wang-oc <TonyWWang-oc@...oxin.com>
To:     <rafael@...nel.org>, <len.brown@...el.com>, <pavel@....cz>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <dave.hansen@...ux.intel.com>, <x86@...nel.org>, <hpa@...or.com>,
        <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <linux-acpi@...r.kernel.org>, <CobeChen@...oxin.com>,
        <TimGuo@...oxin.com>, <LindaChai@...oxin.com>, <LeoLiu@...oxin.com>
Subject: [PATCH] x86/cstate: Replace vendor check with X86_FEATURE_MWAIT in ffh_cstate_init

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@...oxin.com>
---
 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