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/include/linux/virtio.h b/include/linux/virtio.h
index 78408d5..260d1fc 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -45,9 +45,6 @@
* vq: the struct virtqueue we're talking about.
* This returns "false" (and doesn't re-enable) if there are pending
* buffers in the queue, to avoid a race.
- * @shutdown: "unadd" all buffers.
- * vq: the struct virtqueue we're talking about.
- * Remove everything from the queue.
*
* Locking rules are straightforward: the driver is responsible for
* locking. No two operations may be invoked simultaneously.
@@ -67,8 +64,6 @@
void (*disable_cb)(struct virtqueue *vq);
bool (*enable_cb)(struct virtqueue *vq);
-
- void (*shutdown)(struct virtqueue *vq);
};
/**
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 81f828a..d581b29 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -43,6 +43,9 @@
* @set_status: write the status byte
* vdev: the virtio_device
* status: the new status byte
+ * @reset: reset the device
+ * vdev: the virtio device
+ * After this, status and feature negotiation must be done again
* @find_vq: find a virtqueue and instantiate it.
* vdev: the virtio_device
* index: the 0-based virtqueue number in case there's more than one.
@@ -59,6 +62,7 @@
const void *buf, unsigned len);
u8 (*get_status)(struct virtio_device *vdev);
void (*set_status)(struct virtio_device *vdev, u8 status);
+ void (*reset)(struct virtio_device *vdev);
struct virtqueue *(*find_vq)(struct virtio_device *vdev,
unsigned index,
void (*callback)(struct virtqueue *));