[Qemu-devel] [PATCH] virito: unbreak virtio device behinds IOMMU with region cache

[Jason Wang]

Commit c611c76417f5 ("virtio: add MemoryListener to cache ring
translations") registers a memory listener to dma_as. This may not
work when IOMMU is enabled: dma_as(bus_master_as) were correctly
initialized in pcibus_machine_done() after virtio_realize() where we
try to register listener and initialize address space cache.

Fixing this by:

- delay the listener register to status set
- reset dma_as before trying to initialize address spaces to make sure
  it works even IOMMU were created after virtio device

Fixes: c611c76417f5 ("virtio: add MemoryListener to cache ring translations")
Cc: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: Jason Wang <jasow...@redhat.com>
---
 hw/virtio/virtio.c         | 29 ++++++++++++++++++++++++++++-
 include/hw/virtio/virtio.h |  1 +
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 23483c7..179030c 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1084,9 +1084,22 @@ int virtio_set_status(VirtIODevice *vdev, uint8_t val)
             }
         }
     }
+
+    virtio_device_reset_dma_as(vdev);
+
+    if (val == (VIRTIO_CONFIG_S_ACKNOWLEDGE | VIRTIO_CONFIG_S_DRIVER)) {
+        memory_listener_unregister(&vdev->listener);
+        memory_listener_register(&vdev->listener, vdev->dma_as);
+    }
+
     if (k->set_status) {
         k->set_status(vdev, val);
     }
+
+    if (val == 0) {
+        memory_listener_unregister(&vdev->listener);
+    }
+
     vdev->status = val;
     return 0;
 }
@@ -2402,7 +2415,6 @@ static void virtio_device_realize(DeviceState *dev, Error 
**errp)
     }
 
     vdev->listener.commit = virtio_memory_listener_commit;
-    memory_listener_register(&vdev->listener, vdev->dma_as);
 }
 
 static void virtio_device_unrealize(DeviceState *dev, Error **errp)
@@ -2576,6 +2588,21 @@ bool virtio_device_ioeventfd_enabled(VirtIODevice *vdev)
     return virtio_bus_ioeventfd_enabled(vbus);
 }
 
+void virtio_device_reset_dma_as(VirtIODevice *vdev)
+{
+    DeviceState *qdev = DEVICE(vdev);
+    BusState *qbus = BUS(qdev_get_parent_bus(qdev));
+    VirtioBusState *bus = VIRTIO_BUS(qbus);
+    VirtioBusClass *klass = VIRTIO_BUS_GET_CLASS(bus);
+    bool has_iommu = virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM);
+
+    if (klass->get_dma_as != NULL && has_iommu) {
+        vdev->dma_as = klass->get_dma_as(qbus->parent);
+    } else {
+        vdev->dma_as = &address_space_memory;
+    }
+}
+
 static const TypeInfo virtio_device_info = {
     .name = TYPE_VIRTIO_DEVICE,
     .parent = TYPE_DEVICE,
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 15efcf2..f7e0b4a 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -289,6 +289,7 @@ void virtio_queue_aio_set_host_notifier_handler(VirtQueue 
*vq, AioContext *ctx,
                                                 VirtIOHandleAIOOutput 
handle_output);
 VirtQueue *virtio_vector_first_queue(VirtIODevice *vdev, uint16_t vector);
 VirtQueue *virtio_vector_next_queue(VirtQueue *vq);
+void virtio_device_reset_dma_as(VirtIODevice *vdev);
 
 static inline void virtio_add_feature(uint64_t *features, unsigned int fbit)
 {
-- 
2.7.4