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Peter Anvin" Subject: [PATCH v2 1/3] x86: Use MOVL when reading segment registers Date: Fri, 21 Nov 2025 15:14:09 +0100 Message-ID: <20251121141437.205481-1-ubizjak@gmail.com> X-Mailer: git-send-email 2.51.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 Tested-by: Michael Kelley Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "H. Peter Anvin" --- 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__ */ -- 2.51.1