KVM: selftests: Use vcpu_{set,clear}_cpuid_feature() in nVMX state test

Use vcpu_{set,clear}_cpuid_feature() to toggle nested VMX support in the
vCPU CPUID module in the nVMX state test.  Drop CPUID_VMX as there are
no longer any users.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220614200707.3315957-29-seanjc@google.com

tools/testing/selftests/kvm/include/x86_64/processor.h

@@ -160,7 +160,6 @@ struct kvm_x86_cpu_feature {
 #define X86_FEATURE_KVM_MIGRATION_CONTROL	KVM_X86_CPU_FEATURE(0x40000001, 0, EAX, 17)
 
 /* CPUID.1.ECX */
-#define CPUID_VMX		(1ul << 5)
 #define CPUID_XSAVE		(1ul << 26)
 #define CPUID_OSXSAVE		(1ul << 27)
 

tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c

@@ -121,7 +121,7 @@ void test_vmx_nested_state(struct kvm_vcpu *vcpu)
 	test_nested_state(vcpu, state);
 
 	/* Enable VMX in the guest CPUID. */
-	vcpu_set_cpuid(vcpu);
+	vcpu_set_cpuid_feature(vcpu, X86_FEATURE_VMX);
 
 	/*
 	 * Setting vmxon_pa == -1ull and vmcs_pa == -1ull exits early without
@@ -243,22 +243,6 @@ void test_vmx_nested_state(struct kvm_vcpu *vcpu)
 	free(state);
 }
 
-void disable_vmx(struct kvm_vcpu *vcpu)
-{
-	struct kvm_cpuid2 *cpuid = vcpu->cpuid;
-	int i;
-
-	for (i = 0; i < cpuid->nent; ++i)
-		if (cpuid->entries[i].function == 1 &&
-		    cpuid->entries[i].index == 0)
-			break;
-	TEST_ASSERT(i != cpuid->nent, "CPUID function 1 not found");
-
-	cpuid->entries[i].ecx &= ~CPUID_VMX;
-	vcpu_set_cpuid(vcpu);
-	cpuid->entries[i].ecx |= CPUID_VMX;
-}
-
 int main(int argc, char *argv[])
 {
 	struct kvm_vm *vm;
@@ -280,7 +264,7 @@ int main(int argc, char *argv[])
 	/*
 	 * First run tests with VMX disabled to check error handling.
 	 */
-	disable_vmx(vcpu);
+	vcpu_clear_cpuid_feature(vcpu, X86_FEATURE_VMX);
 
 	/* Passing a NULL kvm_nested_state causes a EFAULT. */
 	test_nested_state_expect_efault(vcpu, NULL);