Re: [Qemu-stable] [ANNOUNCE] QEMU 2.6.1 Stable released

[Stefan Hajnoczi]

On Fri, Aug 26, 2016 at 01:45:56PM +0200, Peter Lieven wrote:
> Am 25.08.2016 um 19:23 schrieb Michael Roth:
> > Quoting Peter Lieven (2016-08-25 01:38:13)
> > > 7c509d1 virtio: decrement vq->inuse in virtqueue_discard()
> > > 700f26b virtio: recalculate vq->inuse after migration
> > Looks like these got posted during the freeze :(
> > 
> > > The virtio thing is important because live migration is broken without
> > > the fix as  86cc089 is in 2.6.1.
> > Not sure I understand the relation to 86cc089. Wouldn't the check
> > introduced there always pass due to target initializing inuse to 0?
> > 
> > Or is the issue that the fix introduced in 86cc089 is only partially
> > effective due to inuse not being recalculated properly on target? That might
> > warrant a 2.6.1.1...
> 
> This is what Stefan wrote in the cover letter to the series:
> 
> "I should mention this is for QEMU 2.7. These fixes are needed if the
> CVE-2016-5403 patch has been applied. Without these patches any device that 
> holds VirtQueueElements acros
> live migration will terminate with a "Virtqueue size exceeded" error message. 
> virtio-balloon and virtio-scsi are affected. virtio-bl
> probably too but I haven't tested it."
> 
> Maybe

The virtio inuse fixes are needed for stable (v2.6.2?) so that the
spurious "Virtqueue size exceeded" on migration is solved.

The error can be reproduced when there is a VirtQueueElement pending
across migration (e.g. virtio-blk s->rq failed request list).

Stefan

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