KVM: VMX: Inform user about INTEL_TXT dependency

Inform user to either disable TXT in the BIOS or do TXT launch
with tboot before enabling KVM since some BIOSes do not set
FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX bit when TXT is enabled.
Signed-off-by: Shane Wang <shane.wang@intel.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/vmx.c

@@ -1305,8 +1305,11 @@ static __init int vmx_disabled_by_bios(void)
 			&& tboot_enabled())
 			return 1;
 		if (!(msr & FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX)
-			&& !tboot_enabled())
+			&& !tboot_enabled()) {
+			printk(KERN_WARNING "kvm: disable TXT in the BIOS or "
+				" activate TXT before enabling KVM\n");
 			return 1;
+		}
 	}
 
 	return 0;