From: Uros Bizjak <ubizjak@gmail.com>
To: linux-hyperv@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org
Cc: Uros Bizjak <ubizjak@gmail.com>,
Michael Kelley <mhklinux@outlook.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: [PATCH RESEND v2 1/3] x86: Use MOVL when reading segment registers
Date: Mon, 5 Jan 2026 10:02:32 +0100 [thread overview]
Message-ID: <20260105090422.6243-1-ubizjak@gmail.com> (raw)
Use MOVL when reading segment registers to avoid 0x66 operand-size
override insn prefix. The segment value is always 16-bit and gets
zero-extended to the full 32-bit size.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
---
arch/x86/include/asm/segment.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h
index f59ae7186940..9f5be2bbd291 100644
--- a/arch/x86/include/asm/segment.h
+++ b/arch/x86/include/asm/segment.h
@@ -348,7 +348,7 @@ static inline void __loadsegment_fs(unsigned short value)
* Save a segment register away:
*/
#define savesegment(seg, value) \
- asm("mov %%" #seg ",%0":"=r" (value) : : "memory")
+ asm("movl %%" #seg ",%k0" : "=r" (value) : : "memory")
#endif /* !__ASSEMBLER__ */
#endif /* __KERNEL__ */
--
2.52.0
next reply other threads:[~2026-01-05 9:04 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-05 9:02 Uros Bizjak [this message]
2026-01-05 9:02 ` [PATCH RESEND v2 2/3] x86/hyperv: Use savesegment() instead of inline asm() to save segment registers Uros Bizjak
2026-01-19 16:22 ` H. Peter Anvin
2026-01-05 9:02 ` [PATCH RESEND v2 3/3] x86/hyperv: Remove ASM_CALL_CONSTRAINT with VMMCALL insn Uros Bizjak
2026-01-19 16:23 ` H. Peter Anvin
2026-01-19 16:22 ` [PATCH RESEND v2 1/3] x86: Use MOVL when reading segment registers H. Peter Anvin
2026-01-20 12:08 ` [tip: x86/cleanups] x86/segment: " tip-bot2 for Uros Bizjak
2026-01-20 12:38 ` H. Peter Anvin
2026-01-20 13:47 ` Uros Bizjak
2026-01-20 14:02 ` Uros Bizjak
2026-01-21 11:49 ` Brian Gerst
2026-01-21 14:08 ` David Laight
2026-01-21 16:16 ` Uros Bizjak
2026-01-21 18:55 ` David Laight
2026-03-12 9:30 ` Uros Bizjak
2026-03-12 18:55 ` H. Peter Anvin
2026-03-12 19:38 ` Uros Bizjak
2026-03-12 18:56 ` H. Peter Anvin
2026-03-12 19:11 ` H. Peter Anvin
2026-03-12 19:50 ` Uros Bizjak
2026-03-12 22:01 ` Uros Bizjak
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