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Peter Anvin" Subject: [PATCH 1/2] KVM: VMX: Drop obsolete branch hint prefixes from inline asm Date: Wed, 11 Feb 2026 11:28:49 +0100 Message-ID: <20260211102928.100944-1-ubizjak@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Remove explicit branch hint prefixes (.byte 0x2e / 0x3e) from VMX inline assembly sequences. These prefixes (CS/DS segment overrides used as branch hints on very old x86 CPUs) have been ignored by modern processors for a long time. Keeping them provides no measurable benefit and only enlarges the generated code. No functional change intended. Signed-off-by: Uros Bizjak Cc: Sean Christopherson Cc: Paolo Bonzini Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "H. Peter Anvin" --- arch/x86/kvm/vmx/vmx_ops.h | 3 --- 1 file changed, 3 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx_ops.h b/arch/x86/kvm/vmx/vmx_ops.h index 96677576c836..1000d37f5b0c 100644 --- a/arch/x86/kvm/vmx/vmx_ops.h +++ b/arch/x86/kvm/vmx/vmx_ops.h @@ -119,7 +119,6 @@ static __always_inline unsigned long __vmcs_readl(unsigned long field) #else /* !CONFIG_CC_HAS_ASM_GOTO_OUTPUT */ asm volatile("1: vmread %[field], %[output]\n\t" - ".byte 0x3e\n\t" /* branch taken hint */ "ja 3f\n\t" /* @@ -191,7 +190,6 @@ static __always_inline unsigned long vmcs_readl(unsigned long field) #define vmx_asm1(insn, op1, error_args...) \ do { \ asm goto("1: " __stringify(insn) " %0\n\t" \ - ".byte 0x2e\n\t" /* branch not taken hint */ \ "jna %l[error]\n\t" \ _ASM_EXTABLE(1b, %l[fault]) \ : : op1 : "cc" : error, fault); \ @@ -208,7 +206,6 @@ fault: \ #define vmx_asm2(insn, op1, op2, error_args...) \ do { \ asm goto("1: " __stringify(insn) " %1, %0\n\t" \ - ".byte 0x2e\n\t" /* branch not taken hint */ \ "jna %l[error]\n\t" \ _ASM_EXTABLE(1b, %l[fault]) \ : : op1, op2 : "cc" : error, fault); \ -- 2.53.0