Re: [Qemu-devel] Qemu 2.6 => Qemu 2.7 migration: error while loading state for instance 0x0 of device '0000:00:03.0/virtio-balloon'

[Ladi Prosek <lprosek@redhat.com>]

Hi,

On Tue, Nov 15, 2016 at 11:37 AM, Stefan Priebe - Profihost AG
<s.priebe@profihost.ag> wrote:
> Hello,
>
> Am 15.11.2016 um 11:30 schrieb Dr. David Alan Gilbert:
>> * Stefan Priebe - Profihost AG (s.priebe@profihost.ag) wrote:
>>> Hello,
>>>
>>> today i did a first live migration from Qemu 2.6.2 to Qemu 2.7.0. The VM
>>> is running windows and virtio-balloon and with machine type pc-i440fx-2.5.
>>>
>>> The output of the target qemu process was:
>>> kvm_apic_post_load: Yeh
>>> kvm_apic_post_load: Yeh
>>> kvm_apic_post_load: Yeh
>>> kvm_apic_post_load: Yeh
>>> kvm: VQ 2 size 0x80 < last_avail_idx 0x1 - used_idx 0x4
>>> kvm: error while loading state for instance 0x0 of device
>>> '0000:00:03.0/virtio-balloon'
>>> kvm: load of migration failed: Operation not permitted
>>
>> Yes that's a known bug; only seems to affect windows guests, and I believe
>> doesn't even need to cross versions.
>>
>> There's a bunch of fixes that Stefan applied to virtio code
>> that I think fix this; I see that he cc'd qemu-stable.
>> I think it's 4b7f91ed, but I'm not sure if there are others needed.
>
> thanks for pointing to that commit.
>
> Stefan can you tell me whether it's enough to cherry-pick 4b7f91ed into
> 2.7.0 ?

I don't believe that 4b7f91ed will help here (no device reset on
migration). We've seen this error with QEMU running without:

  commit 4eae2a657d1ff5ada56eb9b4966eae0eff333b0b
  Author: Ladi Prosek <lprosek@redhat.com>
  Date:   Tue Mar 1 12:14:03 2016 +0100

      balloon: fix segfault and harden the stats queue


Is it possible that the VM has run on such a QEMU, then was
live-migrated to 2.6.2, and then to 2.7.0?

Thanks,
Ladi

> Greets,
> Stefan
>
>>
>> Dave
>>>
>>> Greets,
>>> Stefan
>>>
>> --
>> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
>>
>