KVM: x86: Warn about unstable TSC

If creating an SMP guest with unstable host TSC, issue a warning

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 699c6b89c1b48ba7d911d20f2513a868a21313fb..a8dee58e8716010c8a7a9f5d23c0d3ad168e1e0c 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/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);
 }