On Fri, 28 Nov 2014 09:14:46 +0000 Peter Maydell <peter.mayd...@linaro.org> wrote: > On 27 November 2014 at 09:26, Markus Armbruster <arm...@redhat.com> wrote: > > David Gibson <da...@gibson.dropbear.id.au> writes: > > > >> 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. > > > > "[PATCH for-2.2]" would have been a good idea then. Next time :) > > So do you want this patch in 2.2? I was planning to put in the > virtio-vs-xen fixes today and tag rc4, so it's not too late if you're > confident this patch is good. Let me know if you think it should go in, > and I can apply it to master directly. > > -- PMM >
Peter, FWIW I think it should. Commit 3902d49e13c2428bd6381cfdf183103ca4477c1f is clearly bad: virtio-rng does not need the .load callback obviously... and the fact it breaks migration makes it even worse... :( Please apply to 2.2. Cheers. -- Greg
