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virtio: reset function

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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>
This commit is contained in:
Rusty Russell
2008-02-04 23:50:03 -05:00
parent b3369c1fb4
commit 6e5aa7efb2
8 changed files with 87 additions and 32 deletions
Download Patch File Download Diff File Expand all files Collapse all files
drivers/virtio/virtio.c
+10 -2
View File
@@ -102,9 +102,13 @@ static int virtio_dev_remove(struct device *_d)
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 @@ int register_virtio_device(struct virtio_device *dev)
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);
drivers/virtio/virtio_ring.c
-11
View File
@@ -173,16 +173,6 @@ static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
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 @@ static struct virtqueue_ops vring_vq_ops = {
.kick = vring_kick,
.disable_cb = vring_disable_cb,
.enable_cb = vring_enable_cb,
.shutdown = vring_shutdown,
};
struct virtqueue *vring_new_virtqueue(unsigned int num,