linux-kernel - [PATCH 2/7] KVM: VMX: more cleanups to __vmx_vcpu

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Date:   Fri, 28 Oct 2022 19:07:18 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     jmattson@...gle.com, seanjc@...gle.com, jpoimboe@...nel.org
Subject: [PATCH 2/7] KVM: VMX: more cleanups to __vmx_vcpu_run

Slightly improve register allocation, loading vmx only once
before vmlaunch/vmresume.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/vmx/vmenter.S | 40 +++++++++++++++++---------------------
 1 file changed, 18 insertions(+), 22 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
index 1362fe5859f9..0aea6b348a96 100644
--- a/arch/x86/kvm/vmx/vmenter.S
+++ b/arch/x86/kvm/vmx/vmenter.S
@@ -81,13 +81,12 @@ SYM_FUNC_START(__vmx_vcpu_run)
 	 * there must not be any returns or indirect branches between this code
 	 * and vmentry.
 	 */
-	movl VMX_spec_ctrl(%_ASM_DI), %edi
+	movl VMX_spec_ctrl(%_ASM_DI), %eax
 	movl PER_CPU_VAR(x86_spec_ctrl_current), %esi
-	cmp %edi, %esi
+	cmp %eax, %esi
 	je .Lspec_ctrl_done
 	mov $MSR_IA32_SPEC_CTRL, %ecx
 	xor %edx, %edx
-	mov %edi, %eax
 	wrmsr
 
 .Lspec_ctrl_done:
@@ -97,31 +96,28 @@ SYM_FUNC_START(__vmx_vcpu_run)
 	 * an LFENCE to stop speculation from skipping the wrmsr.
 	 */
 
-	/* Load @vmx to RAX. */
-	mov WORD_SIZE(%_ASM_SP), %_ASM_AX
-
 	/* Check if vmlaunch or vmresume is needed */
 	testb $VMX_RUN_VMRESUME, %bl
 
 	/* Load guest registers.  Don't clobber flags. */
-	mov VCPU_RCX(%_ASM_AX), %_ASM_CX
-	mov VCPU_RDX(%_ASM_AX), %_ASM_DX
-	mov VCPU_RBX(%_ASM_AX), %_ASM_BX
-	mov VCPU_RBP(%_ASM_AX), %_ASM_BP
-	mov VCPU_RSI(%_ASM_AX), %_ASM_SI
-	mov VCPU_RDI(%_ASM_AX), %_ASM_DI
+	mov VCPU_RAX(%_ASM_DI), %_ASM_AX
+	mov VCPU_RCX(%_ASM_DI), %_ASM_CX
+	mov VCPU_RDX(%_ASM_DI), %_ASM_DX
+	mov VCPU_RBX(%_ASM_DI), %_ASM_BX
+	mov VCPU_RBP(%_ASM_DI), %_ASM_BP
+	mov VCPU_RSI(%_ASM_DI), %_ASM_SI
 #ifdef CONFIG_X86_64
-	mov VCPU_R8 (%_ASM_AX),  %r8
-	mov VCPU_R9 (%_ASM_AX),  %r9
-	mov VCPU_R10(%_ASM_AX), %r10
-	mov VCPU_R11(%_ASM_AX), %r11
-	mov VCPU_R12(%_ASM_AX), %r12
-	mov VCPU_R13(%_ASM_AX), %r13
-	mov VCPU_R14(%_ASM_AX), %r14
-	mov VCPU_R15(%_ASM_AX), %r15
+	mov VCPU_R8 (%_ASM_DI),  %r8
+	mov VCPU_R9 (%_ASM_DI),  %r9
+	mov VCPU_R10(%_ASM_DI), %r10
+	mov VCPU_R11(%_ASM_DI), %r11
+	mov VCPU_R12(%_ASM_DI), %r12
+	mov VCPU_R13(%_ASM_DI), %r13
+	mov VCPU_R14(%_ASM_DI), %r14
+	mov VCPU_R15(%_ASM_DI), %r15
 #endif
-	/* Load guest RAX.  This kills the @vmx pointer! */
-	mov VCPU_RAX(%_ASM_AX), %_ASM_AX
+	/* Load guest RDI.  This kills the @vmx pointer! */
+	mov VCPU_RDI(%_ASM_DI), %_ASM_DI
 
 	/* Check EFLAGS.ZF from 'testb' above */
 	jz .Lvmlaunch
-- 
2.31.1