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

Gopakumar Choorakkot Edakkunni gopakumar.c.e at gmail.com
Wed Mar 22 06:32:12 CET 2017


Also Yuanhuan, your suggestion about the hugepage mapping / clearing memory
was great .. I tried a test where I just wrote random values into the
entire hugepage area and that succesfully crashed the ovs on the host :).
So thats a good test to generally ensure that the guest doesnt mess up the
host ! Thanks again for your suggestions.

Rgds,
Gopa.

On Sat, Mar 18, 2017 at 4:43 PM, Gopakumar Choorakkot Edakkunni <
gopakumar.c.e at gmail.com> wrote:

> I ended up implementing a mechanism to do the equivalent of a
> vtpci_reset() as soon as the dpdk-app dies and just before it comes back
> up. I am "hoping" that is sufficient to let the host know that the virtio
> rings etc.. are unconfigured, so that when the dpdk app comes up again in
> guest and does hugepage init etc.., it in theory should not confuse the
> host ovs ?
>
> Rgds,
> Gopa.
>
> On Sat, Mar 18, 2017 at 2:37 PM, Gopakumar Choorakkot Edakkunni <
> gopakumar.c.e at gmail.com> wrote:
>
>> I mean vtpci_reset is called from rte_eal_pci_probe() which is the *last*
>> thing in rte_eal_init(), *after* hugepage init, so if I can somehow get
>> that done *before* hugepage init maybe all will be well (because I cant do
>> anything to fix the host side)
>>
>> Rgds,
>> Gopa.
>>
>> On Sat, Mar 18, 2017 at 2:32 PM, Gopakumar Choorakkot Edakkunni <
>> gopakumar.c.e at gmail.com> wrote:
>>
>>> Hi Yuan,
>>>
>>> As a "hack"/"workaround", in rte_eal_init(), if I can call vtpci_reset()
>>> just before rte_eal_memory_init(), that should take care of the problem of
>>> host zeroing out hugepages right ? As of today vtpci_reset() is called in
>>> rte_eal_dev_init() which comes *after* rte_eal_memory_init()
>>>
>>> Rgds,
>>> Gopa.
>>>
>>> On Thu, Mar 16, 2017 at 10:50 PM, Gopakumar Choorakkot Edakkunni <
>>> gopakumar.c.e at gmail.com> wrote:
>>>
>>>> Thanks again Yuanhan, you are the true expert!!
>>>>
>>>> Rgds,
>>>> Gopa.
>>>>
>>>> On Thu, Mar 16, 2017 at 10:40 PM, Yuanhan Liu <
>>>> yuanhan.liu at linux.intel.com> wrote:
>>>>
>>>>> On Thu, Mar 16, 2017 at 10:30:09PM -0700, Gopakumar Choorakkot
>>>>> Edakkunni wrote:
>>>>> > 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 ?
>>>>>
>>>>> Not too much. You might want to hack the guest DPDK EAL memory
>>>>> initiation
>>>>> part though, to not reset the hugepage memory on start. But that's too
>>>>> hacky
>>>>> that I will not recommend you to do so!
>>>>>
>>>>> > 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 ?
>>>>>
>>>>> Yes, backporting the commits I have mentioned should be able to fix it.
>>>>> But please note that I did some code refactorings before those fixes:
>>>>> it
>>>>> won't apply cleanly to DPDK v2.2.
>>>>>
>>>>> And if you want to upgrade, I'd suggest to upgrade to v16.11, which is
>>>>> LTS release.
>>>>>
>>>>>         --yliu
>>>>> >
>>>>> > 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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