KVM: x86: Warn about unstable TSC

If creating an SMP guest with unstable host TSC, issue a warning
Signed-off-by: NZachary Amsden <zamsden@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/x86.c

@@ -5457,6 +5457,10 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
 struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm,
 						unsigned int id)
 {
+	if (check_tsc_unstable() && atomic_read(&kvm->online_vcpus) != 0)
+		printk_once(KERN_WARNING
+		"kvm: SMP vm created on host with unstable TSC; "
+		"guest TSC will not be reliable\n");
 	return kvm_x86_ops->vcpu_create(kvm, id);
 }