KVM/x86: Use 32bit xor to clear registers in svm.c

ubizjak · bonzini · commit 43ce76ce731f · 2018-10-17T19:08:21.000+02:00
x86_64 zero-extends 32bit xor operation to a full 64bit register.

Also add a comment and remove unnecessary instruction suffix in vmx.c

Signed-off-by: Uros Bizjak &lt;ubizjak@gmail.com&gt;
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
@@ -5637,26 +5637,24 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
 		"mov %%r13, %c[r13](%[svm]) \n\t"
 		"mov %%r14, %c[r14](%[svm]) \n\t"
 		"mov %%r15, %c[r15](%[svm]) \n\t"
-#endif
 		/*
 		* Clear host registers marked as clobbered to prevent
 		* speculative use.
 		*/
-		"xor %%" _ASM_BX ", %%" _ASM_BX " \n\t"
-		"xor %%" _ASM_CX ", %%" _ASM_CX " \n\t"
-		"xor %%" _ASM_DX ", %%" _ASM_DX " \n\t"
-		"xor %%" _ASM_SI ", %%" _ASM_SI " \n\t"
-		"xor %%" _ASM_DI ", %%" _ASM_DI " \n\t"
-#ifdef CONFIG_X86_64
-		"xor %%r8, %%r8 \n\t"
-		"xor %%r9, %%r9 \n\t"
-		"xor %%r10, %%r10 \n\t"
-		"xor %%r11, %%r11 \n\t"
-		"xor %%r12, %%r12 \n\t"
-		"xor %%r13, %%r13 \n\t"
-		"xor %%r14, %%r14 \n\t"
-		"xor %%r15, %%r15 \n\t"
+		"xor %%r8d, %%r8d \n\t"
+		"xor %%r9d, %%r9d \n\t"
+		"xor %%r10d, %%r10d \n\t"
+		"xor %%r11d, %%r11d \n\t"
+		"xor %%r12d, %%r12d \n\t"
+		"xor %%r13d, %%r13d \n\t"
+		"xor %%r14d, %%r14d \n\t"
+		"xor %%r15d, %%r15d \n\t"
 #endif
+		"xor %%ebx, %%ebx \n\t"
+		"xor %%ecx, %%ecx \n\t"
+		"xor %%edx, %%edx \n\t"
+		"xor %%esi, %%esi \n\t"
+		"xor %%edi, %%edi \n\t"
 		"pop %%" _ASM_BP
 		:
 		: [svm]"a"(svm),
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
@@ -62,7 +62,7 @@
 
 #define __ex(x) __kvm_handle_fault_on_reboot(x)
 #define __ex_clear(x, reg) \
-	____kvm_handle_fault_on_reboot(x, "xorl " reg " , " reg)
+	____kvm_handle_fault_on_reboot(x, "xor " reg ", " reg)
 
 MODULE_AUTHOR("Qumranet");
 MODULE_LICENSE("GPL");
@@ -11285,6 +11285,10 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
 		"mov %%r13, %c[r13](%0) \n\t"
 		"mov %%r14, %c[r14](%0) \n\t"
 		"mov %%r15, %c[r15](%0) \n\t"
+		/*
+		* Clear host registers marked as clobbered to prevent
+		* speculative use.
+		*/
 		"xor %%r8d,  %%r8d \n\t"
 		"xor %%r9d,  %%r9d \n\t"
 		"xor %%r10d, %%r10d \n\t"
