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

[Michael Roth <mdroth@linux.vnet.ibm.com>]

Quoting Peter Lieven (2016-09-13 10:52:04)
> 
> 
> > Am 13.09.2016 um 17:42 schrieb Stefan Hajnoczi <stefanha@redhat.com>:
> > 
> >> On Thu, Sep 08, 2016 at 03:58:26PM -0500, Michael Roth wrote:
> >> Quoting Stefan Hajnoczi (2016-09-05 12:54:35)
> >>>> 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).
> >> 
> >> Thanks for clarifying. I'm planning to do a 2.6.2 to capture these, the
> >> patches Peter mentioned, and some other fixes that came during 2.7 RC
> >> phase.
> >> 
> >> I have an initial staging tree at:
> >> 
> >>  https://github.com/mdroth/qemu/commits/stable-2.6-staging
> >> 
> >> There's still a few PULLs in flight with patches I plan to pull in, but
> >> hoping to send out the patch round-up early next week and a release the
> >> following week.
> > 
> > Two more candidates for stable:
> > 
> > 4b7f91e virtio: zero vq->inuse in virtio_reset()
> > 104e70c virtio-balloon: discard virtqueue element on reset
> > 
> > They also deal with "Virtqueue size exceeded" errors.
> > 
> > Stefan
> 
> There also seems to be an regression (segfault) in the VNC server in 2.6.1, but i am still investigating.

Do you have a reproducer? I can try a bisect. Trying to get the initial
staging tree posted today but want to make sure any known regressions are
addressed beforehand.

> 
> Peter