linux-kernel - [PATCH 03/10] x86/cpu: Remove unnecessary MwAIT leaf checks

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Message-Id: <20241213205030.9B42B458@davehans-spike.ostc.intel.com>
Date: Fri, 13 Dec 2024 12:50:30 -0800
From: Dave Hansen <dave.hansen@...ux.intel.com>
To: linux-kernel@...r.kernel.org
Cc: x86@...nel.org,tglx@...utronix.de,bp@...en8.de,rafael@...nel.org,lenb@...nel.org,dave.jiang@...el.com,irenic.rajneesh@...il.com,david.e.box@...el.com,Dave Hansen <dave.hansen@...ux.intel.com>
Subject: [PATCH 03/10] x86/cpu: Remove unnecessary MwAIT leaf checks


From: Dave Hansen <dave.hansen@...ux.intel.com>

The CPUID leaf dependency checker will remove X86_FEATURE_MWAIT if
the CPUID level is below the required level (CPUID_MWAIT_LEAF).
Thus, if you check X86_FEATURE_MWAIT you do not need to also
check the CPUID level.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
---

 b/arch/x86/kernel/hpet.c    |    3 ---
 b/arch/x86/kernel/smpboot.c |    2 --
 b/drivers/acpi/acpi_pad.c   |    2 --
 b/drivers/idle/intel_idle.c |    3 ---
 4 files changed, 10 deletions(-)

diff -puN arch/x86/kernel/hpet.c~mwait-leaf-checks-2 arch/x86/kernel/hpet.c
--- a/arch/x86/kernel/hpet.c~mwait-leaf-checks-2	2024-12-13 12:45:33.699090754 -0800
+++ b/arch/x86/kernel/hpet.c	2024-12-13 12:45:33.707091093 -0800
@@ -928,9 +928,6 @@ static bool __init mwait_pc10_supported(
 	if (!cpu_feature_enabled(X86_FEATURE_MWAIT))
 		return false;
 
-	if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
-		return false;
-
 	cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &mwait_substates);
 
 	return (ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) &&
diff -puN arch/x86/kernel/smpboot.c~mwait-leaf-checks-2 arch/x86/kernel/smpboot.c
--- a/arch/x86/kernel/smpboot.c~mwait-leaf-checks-2	2024-12-13 12:45:33.703090924 -0800
+++ b/arch/x86/kernel/smpboot.c	2024-12-13 12:45:33.707091093 -0800
@@ -1292,8 +1292,6 @@ static inline void mwait_play_dead(void)
 		return;
 	if (!this_cpu_has(X86_FEATURE_CLFLUSH))
 		return;
-	if (__this_cpu_read(cpu_info.cpuid_level) < CPUID_MWAIT_LEAF)
-		return;
 
 	eax = CPUID_MWAIT_LEAF;
 	ecx = 0;
diff -puN drivers/acpi/acpi_pad.c~mwait-leaf-checks-2 drivers/acpi/acpi_pad.c
--- a/drivers/acpi/acpi_pad.c~mwait-leaf-checks-2	2024-12-13 12:45:33.703090924 -0800
+++ b/drivers/acpi/acpi_pad.c	2024-12-13 12:45:33.707091093 -0800
@@ -47,8 +47,6 @@ static void power_saving_mwait_init(void
 
 	if (!boot_cpu_has(X86_FEATURE_MWAIT))
 		return;
-	if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
-		return;
 
 	cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
 
diff -puN drivers/idle/intel_idle.c~mwait-leaf-checks-2 drivers/idle/intel_idle.c
--- a/drivers/idle/intel_idle.c~mwait-leaf-checks-2	2024-12-13 12:45:33.703090924 -0800
+++ b/drivers/idle/intel_idle.c	2024-12-13 12:45:33.707091093 -0800
@@ -2317,9 +2317,6 @@ static int __init intel_idle_init(void)
 			return -ENODEV;
 	}
 
-	if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
-		return -ENODEV;
-
 	cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &mwait_substates);
 
 	if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
_