VirtIO devices now remember which endianness they're operating in in order
to support targets which may have guests of either endianness, such as
powerpc. This endianness state is transferred in a subsection of the
virtio device's information.
With virtio-rng this can lead to an abort after a loadvm hitting the
assert() in virtio_is_big_endian(). This can be reproduced by doing a
migrate and load from file on a bi-endian target with a virtio-rng device.
The actual guest state isn't particularly important to triggering this.
The cause is that virtio_rng_load_device() calls virtio_rng_process() which
accesses the ring and thus needs the endianness. However,
virtio_rng_process() is called via virtio_load() before it loads the
subsections. Essentially the ->load callback in VirtioDeviceClass should
only be used for actually reading the device state from the stream, not for
post-load re-initialization.
This patch fixes the bug by moving the virtio_rng_process() after the call
to virtio_load(). Better yet would be to convert virtio to use vmsd and
have the virtio_rng_process() as a post_load callback, but that's a bigger
project for another day.
This is bugfix, and should be considered for the 2.2 branch.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Message-id: 1417067290-20715-1-git-send-email-david@gibson.dropbear.id.au
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
db12451dec