tree 7276a130a2d2eddf84660ec2573298e26611a442
parent fe1a7fe2c4456679b3402f04268bdfafca7b127a
author Michael S. Tsirkin <mst@redhat.com> 1321544475 +0200
committer Rusty Russell <rusty@rustcorp.com.au> 1322102088 +1030

virtio-pci: make reset operation safer

virtio pci device reset actually just does an I/O
write, which in PCI is really posted, that is it
can complete on CPU before the device has received it.

Further, interrupts might have been pending on
another CPU, so device callback might get invoked after reset.

This conflicts with how drivers use reset, which is typically:
	reset
	unregister
a callback running after reset completed can race with
unregister, potentially leading to use after free bugs.

Fix by flushing out the write, and flushing pending interrupts.

This assumes that device is never reset from
its vq/config callbacks, or in parallel with being
added/removed, document this assumption.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>