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

[Flavio Leitner <fbl@redhat.com>]

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