diff --git a/tools/testing/selftests/kvm/x86_64/fix_hypercall_test.c b/tools/testing/selftests/kvm/x86_64/fix_hypercall_test.c
index e0004bd26536..6864eb0d5d14 100644
--- a/tools/testing/selftests/kvm/x86_64/fix_hypercall_test.c
+++ b/tools/testing/selftests/kvm/x86_64/fix_hypercall_test.c
@@ -30,14 +30,11 @@ static uint64_t svm_do_sched_yield(uint8_t apic_id)
 {
 	uint64_t ret;
 
-	asm volatile("mov %1, %%rax\n\t"
-		     "mov %2, %%rbx\n\t"
-		     "svm_hypercall_insn:\n\t"
+	asm volatile("svm_hypercall_insn:\n\t"
 		     "vmmcall\n\t"
-		     "mov %%rax, %0\n\t"
-		     : "=r"(ret)
-		     : "r"((uint64_t)KVM_HC_SCHED_YIELD), "r"((uint64_t)apic_id)
-		     : "rax", "rbx", "memory");
+		     : "=a"(ret)
+		     : "a"((uint64_t)KVM_HC_SCHED_YIELD), "b"((uint64_t)apic_id)
+		     : "memory");
 
 	return ret;
 }
@@ -47,14 +44,11 @@ static uint64_t vmx_do_sched_yield(uint8_t apic_id)
 {
 	uint64_t ret;
 
-	asm volatile("mov %1, %%rax\n\t"
-		     "mov %2, %%rbx\n\t"
-		     "vmx_hypercall_insn:\n\t"
+	asm volatile("vmx_hypercall_insn:\n\t"
 		     "vmcall\n\t"
-		     "mov %%rax, %0\n\t"
-		     : "=r"(ret)
-		     : "r"((uint64_t)KVM_HC_SCHED_YIELD), "r"((uint64_t)apic_id)
-		     : "rax", "rbx", "memory");
+		     : "=a"(ret)
+		     : "a"((uint64_t)KVM_HC_SCHED_YIELD), "b"((uint64_t)apic_id)
+		     : "memory");
 
 	return ret;
 }