Re: [dpdk-stable] [PATCH v16.11 LTS] vhost: protect active rings from async ring changes

[Luca Boccassi <bluca@debian.org>]

On Mon, 2018-03-05 at 13:34 +0100, Maxime Coquelin wrote:
> With up-to-date Yuanhan address.
> 
> On 03/05/2018 01:32 PM, Maxime Coquelin wrote:
> > 
> > 
> > On 03/02/2018 06:28 PM, Luca Boccassi wrote:
> > > On Fri, 2018-03-02 at 18:10 +0100, Maxime Coquelin wrote:
> > > > From: Victor Kaplansky <victork@redhat.com>
> > > > 
> > > > [ backported from upstream commit
> > > > a3688046995f88c518fa27c45b39ae389260b18d ]
> > > > 
> > > > When performing live migration or memory hot-plugging,
> > > > the changes to the device and vrings made by message handler
> > > > done independently from vring usage by PMD threads.
> > > > 
> > > > This causes for example segfaults during live-migration
> > > > with MQ enable, but in general virtually any request
> > > > sent by qemu changing the state of device can cause
> > > > problems.
> > > > 
> > > > These patches fixes all above issues by adding a spinlock
> > > > to every vring and requiring message handler to start operation
> > > > only after ensuring that all PMD threads related to the device
> > > > are out of critical section accessing the vring data.
> > > > 
> > > > Each vring has its own lock in order to not create contention
> > > > between PMD threads of different vrings and to prevent
> > > > performance degradation by scaling queue pair number.
> > > > 
> > > > See https://bugzilla.redhat.com/show_bug.cgi?id=1450680
> > > > 
> > > > Cc: stable@dpdk.org
> > > > Signed-off-by: Victor Kaplansky <victork@redhat.com>
> > > > Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> > > > Acked-by: Yuanhan Liu <yliu@fridaylinux.org>
> > > > 
> > > > Backport conflicts:
> > > >     lib/librte_vhost/vhost.c
> > > >     lib/librte_vhost/vhost.h
> > > >     lib/librte_vhost/vhost_user.c
> > > >     lib/librte_vhost/virtio_net.c
> > > > 
> > > > Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> > > > ---
> > > > 
> > > > Hi Luca, All,
> > > > 
> > > > This is the v16.11 backport for Victor's patch already
> > > > available in
> > > > master and v17.11 LTS. It needed some rework to be applied to
> > > > v16.11.
> > > 
> > > Thank you, applied and pushed to dpdk-stable/16.11.
> > > 
> > 
> > Thanks Luca,
> > 
> > There is another patch that would be applied on top of it, as
> > Victor's
> > patch introduce a regression with Virtio-user. I see it is neither
> > in
> > 16.11 nor 17.11 LTS:
> > 
> > commit 9fce5d0b401fc2c13a860bbbfdebcf85080334e1
> > Author: Maxime Coquelin <maxime.coquelin@redhat.com>
> > Date:   Mon Feb 12 16:46:12 2018 +0100
> > 
> >      vhost: do not take lock on owner reset
> > 
> >      A deadlock happens when handling VHOST_USER_RESET_OWNER
> > request
> >      for the same reason the lock is not taken for
> >      VHOST_USER_GET_VRING_BASE.
> > 
> >      It is safe not to take the lock, as the queues are no more
> > used
> >      by the application when the virtqueues and the device are
> > reset.
> > 
> >      Fixes: a3688046995f ("vhost: protect active rings from async
> > ring 
> > changes")
> >      Cc: stable@dpdk.org
> > 
> >      Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> >      Reviewed-by: Tiwei Bie <tiwei.bie@intel.com>
> >      Reviewed-by: Jianfeng Tan <jianfeng.tan@intel.com>
> > 
> > 
> > Let me know if you want me to post the backport to stable@dpdk.org,
> > or if you can pick it directly from upstream master.
> > 
> > Cheers,
> > Maxime

I can take care of that for 16.11 - have you tested it on top of the
current dpdk-stable/16.11 ? We are in the 11th hour so I want to make
sure any new patches that I pick are tested :-)

-- 
Kind regards,
Luca Boccassi