[PATCH 3/3] virtio: call ->vhost_reset_device() during reset

[Stefan Hajnoczi]

vhost-user-scsi has a VirtioDeviceClass->reset() function that calls
->vhost_reset_device(). The other vhost devices don't notify the vhost
device upon reset.

Stateful vhost devices may need to handle device reset in order to free
resources or prevent stale device state from interfering after reset.

Call ->vhost_device_reset() from virtio_reset() so that that vhost
devices are notified of device reset.

This patch affects behavior as follows:
- vhost-kernel: No change in behavior since ->vhost_reset_device() is
  not implemented.
- vhost-user: back-ends that negotiate
  VHOST_USER_PROTOCOL_F_RESET_DEVICE now receive a
  VHOST_USER_DEVICE_RESET message upon device reset. Otherwise there is
  no change in behavior. DPDK, SPDK, libvhost-user, and the
  vhost-user-backend crate do not negotiate
  VHOST_USER_PROTOCOL_F_RESET_DEVICE automatically.
- vhost-vdpa: an extra SET_STATUS 0 call is made during device reset.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 include/hw/virtio/vhost.h |  3 +++
 hw/scsi/vhost-user-scsi.c | 11 -----------
 hw/virtio/vhost.c         |  9 +++++++++
 hw/virtio/virtio.c        |  4 ++++
 4 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index 6a173cb9fa..381fb51966 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -338,4 +338,7 @@ int vhost_dev_set_inflight(struct vhost_dev *dev,
 int vhost_dev_get_inflight(struct vhost_dev *dev, uint16_t queue_size,
                            struct vhost_inflight *inflight);
 bool vhost_dev_has_iommu(struct vhost_dev *dev);
+
+int vhost_reset_device(struct vhost_dev *hdev);
+
 #endif
diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c
index 8582b2e8ab..6917a748bb 100644
--- a/hw/scsi/vhost-user-scsi.c
+++ b/hw/scsi/vhost-user-scsi.c
@@ -66,16 +66,6 @@ static void vhost_user_scsi_set_status(VirtIODevice *vdev, 
uint8_t status)
     }
 }
 
-static void vhost_user_scsi_reset(VirtIODevice *vdev)
-{
-    VHostSCSICommon *vsc = VHOST_SCSI_COMMON(vdev);
-    struct vhost_dev *dev = &vsc->dev;
-
-    if (dev->vhost_ops->vhost_reset_device) {
-        dev->vhost_ops->vhost_reset_device(dev);
-    }
-}
-
 static void vhost_dummy_handle_output(VirtIODevice *vdev, VirtQueue *vq)
 {
 }
@@ -195,7 +185,6 @@ static void vhost_user_scsi_class_init(ObjectClass *klass, 
void *data)
     vdc->get_features = vhost_scsi_common_get_features;
     vdc->set_config = vhost_scsi_common_set_config;
     vdc->set_status = vhost_user_scsi_set_status;
-    vdc->reset = vhost_user_scsi_reset;
     fwc->get_dev_path = vhost_scsi_common_get_fw_dev_path;
 }
 
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index e2f6ffb446..6003e50e83 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -2087,3 +2087,12 @@ int vhost_net_set_backend(struct vhost_dev *hdev,
 
     return -ENOSYS;
 }
+
+int vhost_reset_device(struct vhost_dev *hdev)
+{
+    if (hdev->vhost_ops->vhost_reset_device) {
+        return hdev->vhost_ops->vhost_reset_device(hdev);
+    }
+
+    return -ENOSYS;
+}
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 4577f3f5b3..d863ffd5d6 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2121,6 +2121,10 @@ void virtio_reset(void *opaque)
         vdev->device_endian = virtio_default_endian();
     }
 
+    if (vdev->vhost_started) {
+        vhost_reset_device(k->get_vhost(vdev));
+    }
+
     if (k->reset) {
         k->reset(vdev);
     }
-- 
2.41.0