Re: [Xen-devel] BUG: jumbo frames broken after commit xen-netfront: Fix race between device setup and open

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

On 06/21/2018 10:05 AM, Juergen Gross wrote:
> On 14/06/18 17:43, Javier Martinez Canillas wrote:
> > Hi Andrew,
> >
> > On Wed, Jun 6, 2018 at 6:29 PM, Andrew Jeddeloh
> > <andrew.jeddeloh@xxxxxxxxxx> wrote:
> > > Hi all,
> > >
> > > The patch "xen-netfront: Fix race between device setup and open" seems
> > > to have introduced a regression preventing setting MTU's larger than
> > > 1500. We experienced this downstream with Container Linux and
> > > confirmed with Fedora 28 as well.
> > >
> > > It's commit f599c64fdf7d9c108e8717fb04bc41c680120da4 in the linux-stable tree.
> > > https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?id=f599c64fdf7d9c108e8717fb04bc41c680120da4
> > >
> > > Downstream bugs:
> > > https://github.com/coreos/bugs/issues/2443
> > > https://bugzilla.redhat.com/show_bug.cgi?id=1584216
> > >
> > > We've confirmed that reverting that commit fixes the bug. It be
> > > reliably can be reproduced on AWS with t2.micro instances (and
> > > presumably other systems using the same driver). Both using
> > > systemd-networkd to set the mtu and manual ip link commands cause the
> > > link to repsond with "Invalid argument" when trying to set the MTU >
> > > 1500.
> > >
> > > I'm not sure why that commit introduced the regression.
> > >
> > > Please let me know if there's any more information that would be helpful.
> > >
> > > - Andrew
> > I'm adding some relevant people to the CC list to bring more attention
> > on this regression.
> >
> > The get_maintainer.pl script is very useful to get some hints on who
> > should be copied, i.e:
> >
> > $ ./scripts/get_maintainer.pl -f drivers/net/xen-netfront.c
> Ross, have you made any progress here? If not I'm thinking of reverting
> your patch as I think the current problem is more severe than the one
> your patch did address.
I've sent a patch today which I believe fixes the issue. Sorry for the 
slow response.
Regards,
--
Ross Lagerwall

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