From: Halil Pasic <pasic@linux.vnet.ibm.com>
To: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>,
QEMU Developers <qemu-devel@nongnu.org>,
Stefan Hajnoczi <stefanha@redhat.com>
Subject: Re: [Qemu-devel] commit virtio: recalculate vq->inuse after migration might cause last_avail_idx vs. used_idx failure
Date: Thu, 15 Dec 2016 12:32:31 +0100 [thread overview]
Message-ID: <b2ad9903-95b4-bf08-f314-c2b250cebb0a@linux.vnet.ibm.com> (raw)
In-Reply-To: <20161215105257.GD2509@work-vm>
On 12/15/2016 11:52 AM, Dr. David Alan Gilbert wrote:
>> We got a bugreport with this log for a live migration target.
>>
>> 2016-12-13T18:59:03.647309Z qemu-system-s390x: VQ 1 size 0x100 < last_avail_idx 0x2f76 - used_idx 0x762f
> Is this actually an endian problem - 2f76 vs 762f ?
>
> Dave
>
Thanks! It seems you are right:
static inline uint16_t vring_avail_idx(VirtQueue *vq)
{
hwaddr pa;
pa = vq->vring.avail + offsetof(VRingAvail, idx);
vq->shadow_avail_idx = virtio_lduw_phys(vq->vdev, pa);
we should have an endiannes handling here before assigning shadow_avail_idx I guess
return vq->shadow_avail_idx;
}
I will meditate a bit more on this and probably create a patch to fix it.
What make me wonder is that according to the reports live migration usually
works (ca 1% fails)...
Can I credit you as reporter in case I end up making a fix?
Halil
next prev parent reply other threads:[~2016-12-15 11:32 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-14 19:12 [Qemu-devel] commit virtio: recalculate vq->inuse after migration might cause last_avail_idx vs. used_idx failure Halil Pasic
2016-12-15 8:24 ` Stefan Hajnoczi
2016-12-15 10:52 ` Dr. David Alan Gilbert
2016-12-15 11:32 ` Halil Pasic [this message]
2016-12-15 11:38 ` Dr. David Alan Gilbert
2016-12-15 13:37 ` Paolo Bonzini
2016-12-15 16:16 ` Halil Pasic
2016-12-15 14:06 ` Stefan Hajnoczi
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