[PATCH 2/2] KVM: VMX: Use LEAVE in vmx_do_interrupt_irqoff()

[Uros Bizjak]

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 <ubizjak@xxxxxxxxx>
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
---
 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
 
-- 
2.49.0