1 files changed, 16 insertions, 0 deletions

diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 2721996bb9c2..912ec5a95e2c 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -770,6 +770,16 @@ kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
         if (ret < 0)
                 goto unlock_fail;
 
+        /* When length is ignored, MMIO is also put on a separate bus, for
+         * faster lookups.
+         */
+        if (!args->len && !(args->flags & KVM_IOEVENTFD_FLAG_PIO)) {
+                ret = kvm_io_bus_register_dev(kvm, KVM_FAST_MMIO_BUS,
+                                              p->addr, 0, &p->dev);
+                if (ret < 0)
+                        goto register_fail;
+        }
+
         kvm->buses[bus_idx]->ioeventfd_count++;
         list_add_tail(&p->list, &kvm->ioeventfds);
 
@@ -777,6 +787,8 @@ kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 
         return 0;
 
+register_fail:
+        kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
 unlock_fail:
         mutex_unlock(&kvm->slots_lock);
 
@@ -816,6 +828,10 @@ kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
                         continue;
 
                 kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
+                if (!p->length) {
+                        kvm_io_bus_unregister_dev(kvm, KVM_FAST_MMIO_BUS,
+                                                  &p->dev);
+                }
                 kvm->buses[bus_idx]->ioeventfd_count--;
                 ioeventfd_release(p);
                 ret = 0;