The following commit has been merged into the x86/asm branch of tip:
Commit-ID: d109ff4f0bc32de354247a6e8ede3ffc8ef14cd0
Gitweb: https://git.kernel.org/tip/d109ff4f0bc32de354247a6e8ede3ffc8ef14cd0
Author: Uros Bizjak <ubizjak@gmail.com>
AuthorDate: Fri, 18 Apr 2025 10:07:44 +02:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Fri, 18 Apr 2025 10:19:25 +02:00
x86/asm: Replace "REP; NOP" with PAUSE mnemonic
Current minimum required version of binutils is 2.25,
which supports PAUSE instruction mnemonic.
Replace "REP; NOP" with this proper mnemonic.
No functional change intended.
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Link: https://lore.kernel.org/r/20250418080805.83679-2-ubizjak@gmail.com
---
arch/x86/boot/boot.h | 2 +-
arch/x86/include/asm/vdso/processor.h | 4 ++--
arch/x86/kernel/relocate_kernel_64.S | 4 ++--
3 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
index 38f17a1..f899717 100644
--- a/arch/x86/boot/boot.h
+++ b/arch/x86/boot/boot.h
@@ -34,7 +34,7 @@
extern struct setup_header hdr;
extern struct boot_params boot_params;
-#define cpu_relax() asm volatile("rep; nop")
+#define cpu_relax() asm volatile("pause")
static inline void io_delay(void)
{
diff --git a/arch/x86/include/asm/vdso/processor.h b/arch/x86/include/asm/vdso/processor.h
index c9b2ba7..240d761 100644
--- a/arch/x86/include/asm/vdso/processor.h
+++ b/arch/x86/include/asm/vdso/processor.h
@@ -7,10 +7,10 @@
#ifndef __ASSEMBLER__
-/* REP NOP (PAUSE) is a good thing to insert into busy-wait loops. */
+/* PAUSE is a good thing to insert into busy-wait loops. */
static __always_inline void rep_nop(void)
{
- asm volatile("rep; nop" ::: "memory");
+ asm volatile("pause" ::: "memory");
}
static __always_inline void cpu_relax(void)
diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index 1d63552..ea604f4 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -405,7 +405,7 @@ SYM_CODE_START_LOCAL_NOALIGN(pr_char_8250)
inb %dx, %al
testb $XMTRDY, %al
jnz .Lready
- rep nop
+ pause
jmp .Lxmtrdy_loop
.Lready:
@@ -426,7 +426,7 @@ SYM_CODE_START_LOCAL_NOALIGN(pr_char_8250_mmio32)
movb (LSR*4)(%rdx), %ah
testb $XMTRDY, %ah
jnz .Lready_mmio
- rep nop
+ pause
jmp .Lxmtrdy_loop_mmio
.Lready_mmio: