vhost_net: device IOTLB support

This patches implements Device IOTLB support for vhost kernel. This is
done through:

1) switch to use dma helpers when map/unmap vrings from vhost codes
2) introduce a set of VhostOps to:
   - setting up device IOTLB request callback
   - processing device IOTLB request
   - processing device IOTLB invalidation
2) kernel support for Device IOTLB API:

- allow vhost-net to query the IOMMU IOTLB entry through eventfd
- enable the ability for qemu to update a specified mapping of vhost
- through ioctl.
- enable the ability to invalidate a specified range of iova for the
  device IOTLB of vhost through ioctl. In x86/intel_iommu case this is
  triggered through iommu memory region notifier from device IOTLB
  invalidation descriptor processing routine.

With all the above, kernel vhost_net can co-operate with userspace
IOMMU. For vhost-user, the support could be easily done on top by
implementing the VhostOps.

Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

include/hw/virtio/vhost.h

@@ -21,6 +21,7 @@ struct vhost_virtqueue {
     unsigned long long used_phys;
     unsigned used_size;
     EventNotifier masked_notifier;
+    struct vhost_dev *dev;
 };
 
 typedef unsigned long vhost_log_chunk_t;
@@ -38,6 +39,7 @@ struct vhost_log {
 
 struct vhost_memory;
 struct vhost_dev {
+    VirtIODevice *vdev;
     MemoryListener memory_listener;
     struct vhost_memory *mem;
     int n_mem_sections;
@@ -62,6 +64,7 @@ struct vhost_dev {
     void *opaque;
     struct vhost_log *log;
     QLIST_ENTRY(vhost_dev) entry;
+    IOMMUNotifier n;
 };
 
 int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
@@ -91,4 +94,5 @@ bool vhost_has_free_slot(void);
 int vhost_net_set_backend(struct vhost_dev *hdev,
                           struct vhost_vring_file *file);
 
+void vhost_device_iotlb_miss(struct vhost_dev *dev, uint64_t iova, int write);
 #endif