[dpdk-dev] virtio "how to restart applications" - //dpdk.org/doc/virtio-net-pmd

Gopakumar Choorakkot Edakkunni gopakumar.c.e at gmail.com
Fri Mar 17 06:30:09 CET 2017


Thanks for the confirmation, glad I reached the person who knows the nuts
and bolts of virtio :-). So if the host is not in our control (ie if I am
just running as a VM on host provided by thirdparty vendor), is there any
workaround I can do from the guest side to prevent problems from happening
on a guest restart ?

And if theres no workarounds at all and the host has to change, instead of
asking the third party vendor to do a wholesale upgrade to 16.04, is there
one/few commits that can be added to the host ovs-dpdk to take care of this
guest restart virtio-reset-before opening case ?

Rgds,
Gopa.

On Thu, Mar 16, 2017 at 10:24 PM, Yuanhan Liu <yuanhan.liu at linux.intel.com>
wrote:

> On Thu, Mar 16, 2017 at 10:20:30PM -0700, Gopakumar Choorakkot Edakkunni
> wrote:
> > >> When I was saying dpdk version, I meant the DPDK version with OVS.
> >
> > Oh I see! My apologies for the misuderstanding. The dpdk version used by
> host
> > ovs should be dpdk2.2, the guest process uses dpdk16.07. The OVS process
> is not
> > getting restarted, what is getting restarted is the guest process using
> > dpdk16.07 - so the above clarifications you had about virtio being
> > reset-before-opened on guest restart - does that still hold good or does
> that
> > need the HOST side dpdk to be 16.04 or above ?
>
> Yes, the HOST dpdk should be >= v16.04.
>
>         --yliu
> >
> > >> And yes, the fixes are not included in the DPDK required for OVS 2.4.
> >
> > Thanks for the info.
> >
> > Rgds,
> > Gopa.
> >
> > On Thu, Mar 16, 2017 at 10:13 PM, Yuanhan Liu <
> yuanhan.liu at linux.intel.com>
> > wrote:
> >
> >     On Thu, Mar 16, 2017 at 09:56:01PM -0700, Gopakumar Choorakkot
> Edakkunni
> >     wrote:
> >     > Hi Yuanhan,
> >     >
> >     > Thanks for the confirmation about not having to do anything
> special to
> >     close
> >     > the ports on dpdk going down or coming up.
> >     >
> >     > As for the question about if I met any issue of ovs getting stuck
> - yes,
> >     my
> >     > guest process runs dpdk 16.07 as I mentioned earlier - and if I
> kill my
> >     guest
> >     > process, then the host OVS-dpdk on the host reports stall ! The
> OVS-dpdk
> >     and
> >     > emu versions I use are as below. But maybe that is because of the
> ovs
> >     missing
> >     > the fixes you mentioned ?
> >
> >     When I was saying dpdk version, I meant the DPDK version with OVS.
> >
> >     > ~# ovs-vswitchd --version
> >     > ovs-vswitchd (Open vSwitch) 2.4.1
> >
> >     And yes, the fixes are not included in the DPDK required for OVS 2.4.
> >
> >             --yliu
> >
> >     > Compiled Nov 14 2016 06:53:31
> >     > # kvm --version
> >     > QEMU emulator version 2.2.0, Copyright (c) 2003-2008 Fabrice
> Bellard
> >     > ~#
> >     >
> >     >
> >     > Rgds,
> >     > Gopa.
> >     >
> >     > On Thu, Mar 16, 2017 at 9:35 PM, Yuanhan Liu <
> yuanhan.liu at linux.intel.com
> >     >
> >     > wrote:
> >     >
> >     >     On Thu, Mar 16, 2017 at 07:48:28PM -0700, Gopakumar Choorakkot
> >     Edakkunni
> >     >     wrote:
> >     >     > Thanks a lot for the response Yuanhan. I am using dpdk
> v16.07. So
> >     what
> >     >     you are
> >     >     > saying is that in 16.07, we dont really need to call
> >     rte_eth_dev_close()
> >     >     on
> >     >     > exit,
> >     >
> >     >     It's not about "don't really need", it's more like "it's hard
> to".
> >     Just
> >     >     think that it may crash at any time.
> >     >
> >     >     > because dpdk will ensure that it will do virtio reset before
> init
> >     when it
> >     >     > comes up right ?
> >     >
> >     >     No, It just handles the abnormal case well when guest APP
> restarts.
> >     >
> >     >     > Regarding the vhost commits you mentioned - do we still need
> those
> >     fixes
> >     >     if we
> >     >     > have the "virtio reset before init" mechanism ?
> >     >
> >     >     Yes, we still need them: just think some malicious guest may
> also
> >     forge
> >     >     data like that.
> >     >
> >     >     I'm a bit confused then. Have you actually met any issue (like
> got
> >     stucked)
> >     >     with DPDK v16.07?
> >     >
> >     >             --yliu
> >     >
> >     >     > Or that is a seperate problem
> >     >     > altogether (and hence we would need those fixes) ?
> >     >     >
> >     >     > Rgds,
> >     >     > Gopa.
> >     >     >
> >     >     > On Thu, Mar 16, 2017 at 7:06 PM, Yuanhan Liu <
> >     yuanhan.liu at linux.intel.com
> >     >     >
> >     >     > wrote:
> >     >     >
> >     >     >     On Thu, Mar 16, 2017 at 12:39:16PM -0700, Gopakumar
> Choorakkot
> >     >     Edakkunni
> >     >     >     wrote:
> >     >     >     > So the doc says we should call rte_eth_dev_close()
> *before*
> >     going
> >     >     down.
> >     >     >     And I
> >     >     >     > know that especially in dpdk-virtionet  in the guest +
> >     ovs-dpdk in
> >     >     the
> >     >     >     host,
> >     >     >     > the ovs ends up getting stalled/stuck (!!) if I dont
> close
> >     the port
> >     >     >     before
> >     >     >     > starting() it when the guest dpdk process comes back
> up.
> >     >     >
> >     >     >     I'm assuming you were using an old version, something
> like dpdk
> >     v2.2?
> >     >     >     IIRC, DPDK v16.04 should have fixed your issue.
> >     >     >
> >     >     >     > Considering that this not done properly can screw up
> the HOST
> >     ovs,
> >     >     and I
> >     >     >     want
> >     >     >     > to do everything possible to avoid that, I want to be
> 200%
> >     sure
> >     >     that I
> >     >     >     call
> >     >     >     > close even if my process gets a kill -9 .. So
> obviously the
> >     only
> >     >     way of
> >     >     >     doing
> >     >     >     > that is to close the port when the dpdk process comes
> back up
> >     and
> >     >     >     *before* we
> >     >     >     > init the port. rte_eth_dev_close() is not capable of
> doing
> >     that as
> >     >     it
> >     >     >     expects
> >     >     >     > the port parameters to be initialized etc.. before it
> can be
> >     >     called.
> >     >     >
> >     >     >     We do virtio reset before init, which is basically what
> >     >     rte_eth_dev_close()
> >     >     >     mainly does. So I see no big issue here.
> >     >     >
> >     >     >     The stuck issue is due to hugepage reset by the guest
> DPDK
> >     >     application,
> >     >     >     leading all virtio vring elements being mem zeroed. The
> old
> >     vhost
> >     >     doesn't
> >     >     >     handle it well, as a result, it got stuck. And here are
> some
> >     relevant
> >     >     >     commits:
> >     >     >
> >     >     >         a436f53 vhost: avoid dead loop chain
> >     >     >         c687b0b vhost: check for ring descriptors overflow
> >     >     >         623bc47 vhost: do sanity check for ring descriptor
> length
> >     >     >
> >     >     >             --yliu
> >     >     >
> >     >     >     > Any other
> >     >     >     > suggestions on what can be done to close on restart
> rather
> >     than
> >     >     close on
> >     >     >     going
> >     >     >     > down ? Thought of bouncing this by the alias before I
> add a
> >     version
> >     >     of
> >     >     >     close
> >     >     >     > myself that can do this close-on-restart
> >     >     >
> >     >     >
> >     >
> >     >
> >
> >
>


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