linux-kernel - [PATCH -tip 2/4] x86/idle: Use MONITOR and MWAIT mnemonics in <asm/mwait.h>

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Message-ID: <20250402180827.3762-2-ubizjak@gmail.com>
Date: Wed,  2 Apr 2025 20:08:06 +0200
From: Uros Bizjak <ubizjak@...il.com>
To: x86@...nel.org,
	linux-kernel@...r.kernel.org
Cc: Uros Bizjak <ubizjak@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH -tip 2/4] x86/idle: Use MONITOR and MWAIT mnemonics in <asm/mwait.h>

Current minimum required version of binutils is 2.25,
which supports MONITOR and MWAIT instruction mnemonics.

Replace the byte-wise specification of MONITOR and
MWAIT with these proper mnemonics.

No functional change intended.

Signed-off-by: Uros Bizjak <ubizjak@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
---
 arch/x86/include/asm/mwait.h | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h
index 3377869ff2e8..006b150bcb5f 100644
--- a/arch/x86/include/asm/mwait.h
+++ b/arch/x86/include/asm/mwait.h
@@ -27,9 +27,7 @@
 
 static __always_inline void __monitor(const void *eax, u32 ecx, u32 edx)
 {
-	/* "monitor %eax, %ecx, %edx;" */
-	asm volatile(".byte 0x0f, 0x01, 0xc8;"
-		     :: "a" (eax), "c" (ecx), "d"(edx));
+	asm volatile("monitor %0, %1, %2" :: "a" (eax), "c" (ecx), "d" (edx));
 }
 
 static __always_inline void __monitorx(const void *eax, u32 ecx, u32 edx)
@@ -43,9 +41,7 @@ static __always_inline void __mwait(u32 eax, u32 ecx)
 {
 	mds_idle_clear_cpu_buffers();
 
-	/* "mwait %eax, %ecx;" */
-	asm volatile(".byte 0x0f, 0x01, 0xc9;"
-		     :: "a" (eax), "c" (ecx));
+	asm volatile("mwait %0, %1" :: "a" (eax), "c" (ecx));
 }
 
 /*
@@ -95,9 +91,8 @@ static __always_inline void __mwaitx(u32 eax, u32 ebx, u32 ecx)
 static __always_inline void __sti_mwait(u32 eax, u32 ecx)
 {
 	mds_idle_clear_cpu_buffers();
-	/* "mwait %eax, %ecx;" */
-	asm volatile("sti; .byte 0x0f, 0x01, 0xc9;"
-		     :: "a" (eax), "c" (ecx));
+
+	asm volatile("sti; mwait %0, %1" :: "a" (eax), "c" (ecx));
 }
 
 /*
-- 
2.42.0