Re: [Qemu-devel] vhost-user breaks after 96a3d98.

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jan 03, 2017 at 03:33:12PM -0200, Flavio Leitner wrote:
> On Tue, 3 Jan 2017 18:28:18 +0800
> Jason Wang <jasowang@redhat.com> wrote:
> 
> > On 2017年01月03日 11:09, Jason Wang wrote:
> > >
> > >
> > > On 2016年12月30日 20:41, Flavio Leitner wrote:  
> > >> Hi,
> > >>
> > >> While I was testing vhost-user using OVS 2.5 and DPDK 2.2.0 in the
> > >> host and testpmd dpdk 2.2.0 in the guest, I found that the commit
> > >> below breaks the environment and no packets gets into the guest.
> > >>
> > >> dpdk port --> OVS --> vhost-user --> guest --> testpmd
> > >>                           ^--- drops here         ^--- no packets here.
> > >>
> > >> commit 96a3d98d2cdbd897ff5ab33427aa4cfb94077665
> > >> Author: Jason Wang <jasowang@redhat.com>
> > >> Date:   Mon Aug 1 16:07:58 2016 +0800
> > >>
> > >>      vhost: don't set vring call if no vector
> > >>           We used to set vring call fd unconditionally even if guest 
> > >> driver does
> > >>      not use MSIX for this vritqueue at all. This will cause lots of
> > >>      unnecessary userspace access and other checks for drivers does 
> > >> not use
> > >>      interrupt at all (e.g virtio-net pmd). So check and clean vring 
> > >> call
> > >>      fd if guest does not use any vector for this virtqueue at
> > >>      all.
> > >> [...]
> > >>
> > >> Thanks,  
> > >
> > > Hi Flavio:
> > >
> > > Thanks for reporting this issue, could this be a bug of vhost-user? (I 
> > > believe virito-net pmd does not use interrupt for rx/tx at all)
> > >
> > > Anyway, will try to reproduce it.
> > >  
> > 
> > Could not reproduce this issue on similar setups (the only difference is 
> > I don't create dpdk port) with dpdk 16.11 and ovs.git HEAD. Suspect an 
> > issue dpdk. Will try OVS 2.5 + DPDK 2.2.0.
> 
> Yeah, that's the combo I am testing and seeing the issue.  I found the
> commit after bisecting qemu and then confirmed by testing up to the
> previous commit (works okay) and then the commit above (fails).
> 
> I still have my test environment available, so I would be able to test
> any patch you might have.
> 
> Thanks,
> -- 
> Flavio

Could you pls try to test dpdk git head and bisect that to find
what fixes the issue?

-- 
MST