tree 060a955e711ac224136157a5410e88dcdab965af
parent b3369c1fb410fddeb38a404316c861395f6d6ae8
author Rusty Russell <rusty@rustcorp.com.au> 1202187003 -0500
committer Rusty Russell <rusty@rustcorp.com.au> 1202129403 +1100

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>