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([193.77.86.199]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5f36ee55212sm4435244a12.9.2025.04.14.01.11.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Apr 2025 01:11:35 -0700 (PDT) From: Uros Bizjak To: kvm@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org Cc: Uros Bizjak , Sean Christopherson , Paolo Bonzini , Vitaly Kuznetsov , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" Subject: [PATCH 2/2] KVM: VMX: Use LEAVE in vmx_do_interrupt_irqoff() Date: Mon, 14 Apr 2025 10:10:51 +0200 Message-ID: <20250414081131.97374-2-ubizjak@gmail.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250414081131.97374-1-ubizjak@gmail.com> References: <20250414081131.97374-1-ubizjak@gmail.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Micro-optimize vmx_do_interrupt_irqoff() by substituting MOV %RBP,%RSP; POP %RBP instruction sequence with equivalent LEAVE instruction. GCC compiler does this by default for a generic tuning and for all modern processors: DEF_TUNE (X86_TUNE_USE_LEAVE, "use_leave", m_386 | m_CORE_ALL | m_K6_GEODE | m_AMD_MULTIPLE | m_ZHAOXIN | m_TREMONT | m_CORE_HYBRID | m_CORE_ATOM | m_GENERIC) The new code also saves a couple of bytes, from: 27: 48 89 ec mov %rbp,%rsp 2a: 5d pop %rbp to: 27: c9 leave No functional change intended. Signed-off-by: Uros Bizjak Cc: Sean Christopherson Cc: Paolo Bonzini Cc: Vitaly Kuznetsov Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "H. Peter Anvin" --- arch/x86/kvm/vmx/vmenter.S | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S index f6986dee6f8c..0a6cf5bff2aa 100644 --- a/arch/x86/kvm/vmx/vmenter.S +++ b/arch/x86/kvm/vmx/vmenter.S @@ -59,8 +59,7 @@ * without the explicit restore, thinks the stack is getting walloped. * Using an unwind hint is problematic due to x86-64's dynamic alignment. */ - mov %_ASM_BP, %_ASM_SP - pop %_ASM_BP + leave RET .endm