KVM: Add PV MSR to enable asynchronous page faults delivery.

Guest enables async PF vcpu functionality using this MSR.

Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index e674820..ee4314e 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -93,6 +93,7 @@
 void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu);
 int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,
 		       struct kvm_arch_async_pf *arch);
+int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu);
 #endif
 
 struct kvm_vcpu {