[PATCH v3] doc: fix vhost multi-queue reconnection

[Ding, Xuan]

Hi Chenbo,

> -----Original Message-----
> From: Xia, Chenbo <chenbo.xia at intel.com>
> Sent: Friday, May 6, 2022 4:41 PM
> To: Ding, Xuan <xuan.ding at intel.com>; maxime.coquelin at redhat.com
> Cc: dev at dpdk.org; Hu, Jiayu <jiayu.hu at intel.com>; stable at dpdk.org
> Subject: RE: [PATCH v3] doc: fix vhost multi-queue reconnection
> 
> > -----Original Message-----
> > From: Ding, Xuan <xuan.ding at intel.com>
> > Sent: Friday, April 15, 2022 10:08 AM
> > To: maxime.coquelin at redhat.com; Xia, Chenbo <chenbo.xia at intel.com>
> > Cc: dev at dpdk.org; Hu, Jiayu <jiayu.hu at intel.com>; Ding, Xuan
> > <xuan.ding at intel.com>; stable at dpdk.org
> > Subject: [PATCH v3] doc: fix vhost multi-queue reconnection
> >
> > From: Xuan Ding <xuan.ding at intel.com>
> >
> > Since QEMU 5.2.0 fixes the vhost split ring multi-queue reconnection
> > issue in commit f66337bdbfda ("vhost-user: save features of
> > multiqueues if chardev is closed"), this patch updates known issue to
> > indicate the range of affeacted QEMU versions.
> >
> > Fixes: b37e95507e1b ("doc: add vhost multi-queue reconnection issue")
> > Cc: stable at dpdk.org
> >
> > Signed-off-by: Xuan Ding <xuan.ding at intel.com>
> > ---
> > v3:
> > * Updated affected QEMU versions.
> >
> > v2:
> > * Add fixes in commit title and log.
> > ---
> >  doc/guides/rel_notes/known_issues.rst | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/doc/guides/rel_notes/known_issues.rst
> > b/doc/guides/rel_notes/known_issues.rst
> > index 187d9c942e..bd89d58d24 100644
> > --- a/doc/guides/rel_notes/known_issues.rst
> > +++ b/doc/guides/rel_notes/known_issues.rst
> > @@ -885,14 +885,15 @@ Unsuitable IOVA mode may be picked as the
> > default
> >  **Driver/Module**:
> >     ALL.
> >
> > -Vhost multi-queue reconnection failed with QEMU version >= 4.2.0
> > -----------------------------------------------------------------
> > +Vhost multi-queue reconnection failed with QEMU version 4.2.0 to
> > +5.1.0-
> > rc3
> 
> So 5.1.0 fixes the problem or not? As 5.1.0 is later than 5.1.0-rc3 but you said
> from 5.2.0 it's fixed. And I think we should just mention formal release, not
> any rc, qemu users should not use any rc for formal usage.

Thanks for your catch. The tag here is wrong(actually 5.2.0-rc0).
So the actual fixed version is in 5.2.0. I will fix it in next version.

Regards,
Xuan

> 
> Thanks,
> Chenbo
> 
> > +---------------------------------------------------------------------
> > +----
> > -
> >
> >  **Description**
> >     It's a QEMU regression bug (bad commit: c6beefd674ff). QEMU only
> saves
> >     acked features for one vhost-net when vhost quits. When vhost
> > reconnects
> >     to virtio-net/virtio-pmd in multi-queue situations, the features been
> > -   set multiple times are not consistent.
> > +   set multiple times are not consistent. QEMU-5.2.0 fixes this issue
> > + in
> > commit
> > +   f66337bdbfda ("vhost-user: save features of multiqueues if chardev
> > + is
> > closed").
> >
> >  **Implication**
> >     Vhost cannot reconnect back to virtio-net/virtio-pmd normally.
> > --
> > 2.17.1