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Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_m
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table. |
Date: |
Sun, 14 Aug 2016 05:44:23 +0300 |
On Sat, Aug 13, 2016 at 02:13:46AM -0400, Marc-André Lureau wrote:
> Hi
>
> ----- Original Message -----
> > On Fri, Aug 12, 2016 at 11:54:54AM -0400, Marc-André Lureau wrote:
> > > Hi
> > >
> > > ----- Original Message -----
> > > > On Fri, Aug 12, 2016 at 03:20:56AM -0400, Marc-André Lureau wrote:
> > > > > Hi
> > > > >
> > > > > ----- Original Message -----
> > > > > > sent a follow-up response to GET_FEATURES), I am now wondering if
> > > > > > this
> > > > > > patch
> > > > > > may break existing vhost applications too ? If so, reverting it
> > > > > > possibly
> > > > > > better.
> > > > > > What confuses me is why it doesn’t fail all the time, but only about
> > > > > > 20%
> > > > > > to
> > > > > > 30% time as Fam reports.
> > > > > >
> > > > > > Thoughts : Michael, Fam, MarcAndre ?
> > > > >
> > > > > Indeed, I didn't ack that patch in the first place for that kind of
> > > > > reasons, so I would revert it.
> > > > >
> > > > > thanks
> > > >
> > > > I guess that's the safest thing to do for 2.7.
> > > > At least that's not any worse than 2.6.
> > > > I still think it's a good idea long term and test should be fixed,
> > > > but let's revert for now.
> > > >
> > >
> > > What about other backends that may have similar expectations from the
> > > protocol.
> > >
> > > This patch is a hack, there is no reason to have it upstream.
> >
> > The reason is to avoid crashes with existing backends.
>
> Which backend? I had a similar issue, it wasn't about crashes, and Prerna
> didn't mention crashes either, but anyway there is not guarantee that adding
> a GET_FEATURES message will solve it...
>
So what bothers me the most about dropping this is that
there are no backends with the new feature implemented
at the moment.
The GET_FEATURES hack at least makes it easy to test
with existing backends ...
> > > The solution is provided with the REPLY_ACK patch.
> >
> > It needs a backend update though.
> >
> > But the issue is old, it's not a regression. I think we lose nothing
> > by pushing the work-around out until after 2.7.
> >
> > --
> > MST
> >
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table., (continued)
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table., Prerna Saxena, 2016/08/12
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table., Marc-André Lureau, 2016/08/12
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table., Peter Maydell, 2016/08/12
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table., Michael S. Tsirkin, 2016/08/12
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table., Peter Maydell, 2016/08/15
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table., Michael S. Tsirkin, 2016/08/12
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table., Marc-André Lureau, 2016/08/12
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table., Michael S. Tsirkin, 2016/08/12
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table., Marc-André Lureau, 2016/08/13
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table., Michael S. Tsirkin, 2016/08/13
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table.,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table., Michael S. Tsirkin, 2016/08/13
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table., Prerna Saxena, 2016/08/14
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table., Michael S. Tsirkin, 2016/08/14
- Re: [Qemu-devel] [PULL 3/3] vhost-user: Attempt to fix a race with set_mem_table., Maxime Coquelin, 2016/08/31
Re: [Qemu-devel] [PULL 0/3] virtio/vhost: fixes, Peter Maydell, 2016/08/10