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

[Peter Lieven]

> Am 13.09.2016 um 20:04 schrieb Michael Roth <address@hidden>:
> 
> Quoting Peter Lieven (2016-09-13 10:52:04)
>> 
>> 
>>>> Am 13.09.2016 um 17:42 schrieb Stefan Hajnoczi <address@hidden>:
>>>> 
>>>> 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.

i am out of Office till Monday, but if I remember correctly I saw mutex errors 
(not segfaults) with 2.6.1 that were not there on 2.5.1.1. They happened while 
my colleagues where experimenting with a new VNC client. So its likely that a 
certain connect/disconnect pattern is the trigger. I am not sure if the same 
issue exists in master. For more details we might have to wait till i am back 
at the office, sorry.

However, CC'ing Jan from Kamp. Maybe he has a reproducer.

Peter