virtio: reset function
A reset function solves three problems:
1) It allows us to renegotiate features, eg. if we want to upgrade a
guest driver without rebooting the guest.
2) It gives us a clean way of shutting down virtqueues: after a reset,
we know that the buffers won't be used by the host, and
3) It helps the guest recover from messed-up drivers.
So we remove the ->shutdown hook, and the only way we now remove
feature bits is via reset.
We leave it to the driver to do the reset before it deletes queues:
the balloon driver, for example, needs to chat to the host in its
remove function.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 303cb6f..7dddb18 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -102,9 +102,13 @@
struct virtio_driver *drv = container_of(dev->dev.driver,
struct virtio_driver, driver);
- dev->config->set_status(dev, dev->config->get_status(dev)
- & ~VIRTIO_CONFIG_S_DRIVER);
drv->remove(dev);
+
+ /* Driver should have reset device. */
+ BUG_ON(dev->config->get_status(dev));
+
+ /* Acknowledge the device's existence again. */
+ add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
return 0;
}
@@ -130,6 +134,10 @@
dev->dev.bus = &virtio_bus;
sprintf(dev->dev.bus_id, "%u", dev->index);
+ /* We always start by resetting the device, in case a previous
+ * driver messed it up. This also tests that code path a little. */
+ dev->config->reset(dev);
+
/* Acknowledge that we've seen the device. */
add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index dbe1d35..9849bab 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -173,16 +173,6 @@
vq->num_free++;
}
-/* FIXME: We need to tell other side about removal, to synchronize. */
-static void vring_shutdown(struct virtqueue *_vq)
-{
- struct vring_virtqueue *vq = to_vvq(_vq);
- unsigned int i;
-
- for (i = 0; i < vq->vring.num; i++)
- detach_buf(vq, i);
-}
-
static inline bool more_used(const struct vring_virtqueue *vq)
{
return vq->last_used_idx != vq->vring.used->idx;
@@ -278,7 +268,6 @@
.kick = vring_kick,
.disable_cb = vring_disable_cb,
.enable_cb = vring_enable_cb,
- .shutdown = vring_shutdown,
};
struct virtqueue *vring_new_virtqueue(unsigned int num,