5 files changed, 23 insertions, 0 deletions
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 1f68c5831924..eb3f2b1b764c 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5528,6 +5528,10 @@ static int handle_ept_misconfig(struct kvm_vcpu *vcpu)
        gpa_t gpa;
        gpa = vmcs_read64(GUEST_PHYSICAL_ADDRESS);
+        if (!kvm_io_bus_write(vcpu->kvm, KVM_FAST_MMIO_BUS, gpa, 0, NULL)) {
+                skip_emulated_instruction(vcpu);
+                return 1;
+        }
        ret = handle_mmio_page_fault_common(vcpu, gpa, true);
        if (likely(ret == RET_MMIO_PF_EMULATE))
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 7d21cf9f4380..6c3c2eb96d06 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -163,6 +163,7 @@ enum kvm_bus {
        KVM_MMIO_BUS,
        KVM_PIO_BUS,
        KVM_VIRTIO_CCW_NOTIFY_BUS,
+        KVM_FAST_MMIO_BUS,
        KVM_NR_BUSES
 };
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 39098a61f41c..d8a6ce4c2a83 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -515,6 +515,7 @@ enum {
        kvm_ioeventfd_flag_nr_pio,
        kvm_ioeventfd_flag_nr_deassign,
        kvm_ioeventfd_flag_nr_virtio_ccw_notify,
+        kvm_ioeventfd_flag_nr_fast_mmio,
        kvm_ioeventfd_flag_nr_max,
 };
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;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 56baae8c2f56..96456ac888ba 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2922,6 +2922,7 @@ static int __kvm_io_bus_read(struct kvm_io_bus *bus, struct kvm_io_range *range,
        return -EOPNOTSUPP;
 }
+EXPORT_SYMBOL_GPL(kvm_io_bus_write);
 /* kvm_io_bus_read - called under kvm->slots_lock */
 int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,