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

Yuanhan Liu yuanhan.liu at linux.intel.com
Fri Mar 17 06:24:33 CET 2017


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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