Re: [Qemu-devel] [Qemu-stable] Patch Round-up for stable 2.1.1, freeze on 2014-09-03

[Andrey Korolyov]

On Wed, Sep 3, 2014 at 12:13 PM, Michael S. Tsirkin <address@hidden> wrote:
> On Wed, Sep 03, 2014 at 11:43:54AM +0400, Andrey Korolyov wrote:
>> On Wed, Sep 3, 2014 at 10:10 AM, Michael S. Tsirkin <address@hidden> wrote:
>> > On Wed, Sep 03, 2014 at 02:17:02AM +0400, Andrey Korolyov wrote:
>> >> On Wed, Sep 3, 2014 at 2:09 AM, Andrey Korolyov <address@hidden> wrote:
>> >> > On Wed, Sep 3, 2014 at 1:51 AM, Michael S. Tsirkin <address@hidden> 
>> >> > wrote:
>> >> >> On Wed, Sep 03, 2014 at 01:29:29AM +0400, Andrey Korolyov wrote:
>> >> >>> On Wed, Sep 3, 2014 at 1:03 AM, Michael S. Tsirkin <address@hidden> 
>> >> >>> wrote:
>> >> >>> >> bad one is the
>> >> >>> >>
>> >> >>> >> Author: Jason Wang <address@hidden>
>> >> >>> >> Date:   Tue Sep 2 18:07:46 2014 +0300
>> >> >>> >>
>> >> >>> >>     vhost_net: start/stop guest notifiers properly
>> >> >>> >
>> >> >>> >
>> >> >>> >
>> >> >>> > upstream has this (pull request sent today):
>> >> >>> > vhost_net: cleanup start/stop condition
>> >> >>> >
>> >> >>> > Could you apply it and see if it helps please?
>> >> >>> >
>> >> >>> > Michael, if it helps it should be before start/stop guest notifiers
>> >> >>> > ideally to avoid bisect problems.
>> >> >>>
>> >> >>> It is already applied as shown from the list in the previous message
>> >> >>> (there are some aio fixes too on top of 2.1 I picked before but they
>> >> >>> should not impact vhost-net interaction in any mean). The symptoms are
>> >> >>> a bit interesting - VM crashes only at PCI device initalization (e.g.
>> >> >>> grub stage after reset and initrd unpacking are passing well, but then
>> >> >>> things getting ugly). I am running 3.14 guest i686-pae kernel from
>> >> >>> debian backports in guest, so it may be version-specific after all. If
>> >> >>> it`ll be hard to reproduce, I can try 64bit, expecting same behavior.
>> >> >>> Please find args in attached file.
>> >> >>
>> >> >>
>> >> >>
>> >> >> ok just to make sure - which tree do I clone exactly?
>> >> >>
>> >> >
>> >> > https://github.com/mdroth/qemu.git stable-2.1-staging showing same
>> >> > behavior for me with those patches
>> >>
>> >> Forgot to mention important detail - I am playing with -mq now, so
>> >> actually virtio-net working in a bit different way than it may
>> >> expected (it also shown in args list from above, but someone may miss
>> >> it):
>> >> ...
>> >> qemu-system-x86_64: unable to start vhost net: 95: falling back on
>> >> userspace virtio
>> >> qemu-system-x86_64: unable to start vhost net: 95: falling back on
>> >> userspace virtio
>> >> ...
>> >
>> >
>> > OK I see at least one obvious bug there: does the following fix the
>> > crash for you?
>> > Separately, we need to debug why mq vhost is broken for you.
>> > Is this a regression?
>> >
>> > diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
>> > index ba5d544..1fe18c7 100644
>> > --- a/hw/net/vhost_net.c
>> > +++ b/hw/net/vhost_net.c
>> > @@ -289,7 +289,7 @@ int vhost_net_start(VirtIODevice *dev, NetClientState 
>> > *ncs,
>> >      BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(dev)));
>> >      VirtioBusState *vbus = VIRTIO_BUS(qbus);
>> >      VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(vbus);
>> > -    int r, i = 0;
>> > +    int r, i;
>> >
>> >      if (!vhost_net_device_endian_ok(dev)) {
>> >          error_report("vhost-net does not support cross-endian");
>> > @@ -317,16 +317,22 @@ int vhost_net_start(VirtIODevice *dev, 
>> > NetClientState *ncs,
>> >          r = vhost_net_start_one(get_vhost_net(ncs[i].peer), dev);
>> >
>> >          if (r < 0) {
>> > -            goto err;
>> > +            goto err_start;
>> >          }
>> >      }
>> >
>> >      return 0;
>> >
>> > -err:
>> > +err_start:
>> >      while (--i >= 0) {
>> >          vhost_net_stop_one(get_vhost_net(ncs[i].peer), dev);
>> >      }
>> > +err:
>> > +    r = k->set_guest_notifiers(qbus->parent, total_queues * 2, false);
>> > +    if (r < 0) {
>> > +        fprintf(stderr, "vhost guest notifier cleanup failed: %d\n", r);
>> > +        fflush(stderr);
>> > +    }
>> >      return r;
>> >  }
>> >
>>
>>
>> another bits of information:
>>  - the userspace fallback is not specific to mq (very unfortunately
>> for me because I didn`t checked this exact regression week before when
>> I saw it for mq and it is not specific for queued patches for 2.1.1),
>>  - bug itself is not specific to mq, reproduces every time even with
>> more generic interface config without queues,
>>  - patch from above does not fix the issue.
>>
>> Strace output for all threads is available at
>> http://xdel.ru/downloads/qemu.out.gz, attached just before reset.
>
>
>
> OK does my patch help?
>
> Jason sent patches to fix the fallback to virtio bug -
> does that work for you?
>

Whoops, missed patch from Jason, meant yours above. The acceleration
is fixed, thanks! Jason`s patch alone fixes both crash appearance and
accel initialization while yours fixed initialization (while intended
to fix assert appearance), with crash still in place.