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Fix for crash after migration in virtio-rng on bi-endian targets

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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>
This commit is contained in:
David Gibson 2014-11-27 16:48:10 +11:00 committed by Peter Maydell
parent 771b6ed37e
commit db12451dec
1 changed files with 8 additions and 7 deletions
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15
hw/virtio/virtio-rng.c
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@ -113,20 +113,22 @@ static void virtio_rng_save(QEMUFile *f, void *opaque)
static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
{
VirtIORNG *vrng = opaque;
int ret;
if (version_id != 1) {
return -EINVAL;
}
return virtio_load(VIRTIO_DEVICE(opaque), f, version_id);
}
ret = virtio_load(VIRTIO_DEVICE(vrng), f, version_id);
if (ret != 0) {
return ret;
}
static int virtio_rng_load_device(VirtIODevice *vdev, QEMUFile *f,
int version_id)
{
/* We may have an element ready but couldn't process it due to a quota
* limit. Make sure to try again after live migration when the quota may
* have been reset.
*/
virtio_rng_process(VIRTIO_RNG(vdev));
virtio_rng_process(vrng);
return 0;
}
@ -231,7 +233,6 @@ static void virtio_rng_class_init(ObjectClass *klass, void *data)
vdc->realize = virtio_rng_device_realize;
vdc->unrealize = virtio_rng_device_unrealize;
vdc->get_features = get_features;
vdc->load = virtio_rng_load_device;
}
static void virtio_rng_initfn(Object *obj)