KVM: eVMCS: check if nesting is enabled

In the next patch nested_get_evmcs_version will be always set in kvm_x86_ops for
VMX, even if nesting is disabled.  Therefore, check whether VMX (aka nesting)
is available in the function, the caller will not do the check anymore.
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/evmcs.c

@@ -4,6 +4,7 @@
 #include <linux/smp.h>
 
 #include "../hyperv.h"
+#include "../cpuid.h"
 #include "evmcs.h"
 #include "vmcs.h"
 #include "vmx.h"
@@ -333,7 +334,8 @@ uint16_t nested_get_evmcs_version(struct kvm_vcpu *vcpu)
 	 * maximum supported version. KVM supports versions from 1 to
 	 * KVM_EVMCS_VERSION.
 	 */
-       if (vmx->nested.enlightened_vmcs_enabled)
+	if (kvm_cpu_cap_get(X86_FEATURE_VMX) &&
+	    vmx->nested.enlightened_vmcs_enabled)
 		return (KVM_EVMCS_VERSION << 8) | 1;
 
 	return 0;