Re: [Xen-devel] Xen-unstable Linux 3.14-rc3 and 3.13 Network troubles "bisected"

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Mar 11, 2014 at 12:38:07PM +0000, Wei Liu wrote:
> On Tue, Mar 11, 2014 at 01:31:42PM +0100, Sander Eikelenboom wrote:
> > 
> > Tuesday, March 11, 2014, 11:19:48 AM, you wrote:
> > 
> > > On Tue, Mar 11, 2014 at 12:00:26AM +0100, Sander Eikelenboom wrote:
> > > [...]
> > >> 
> > >> >> Wei.
> > >> 
> > >> Hi Paul,
> > >> 
> > >> It seems a commit by you: "ca2f09f2b2c6c25047cfc545d057c4edfcfe561c 
> > >> xen-netback: improve guest-receive-side flow control"
> > >> is the first that gives the Bad grant references.
> > >> It seems later patches partly prevent or mask the issue, so it is less 
> > >> easy to trigger it.
> > >> With only this commit applied i can trigger it quite fast.
> > >> 
> > >> This is the result of:
> > >> - First testing a baseline that worked o.k. for several days (3.13.6 for 
> > >> both dom0 and domU)
> > >> - Testing domU 3.14-rc5 and dom0 3.13.6, this worked ok.
> > >> - Testing dom0 3.14-rc5 and domU 3.13.6, this failed.
> > >> - After that took 3.13.6 as base and first applied all the general xen 
> > >> related patches for the dom0 kernel, that works ok.
> > >> - After that started to apply the netback changes for 3.14 and that 
> > >> failed after the commit stated above.
> > >> 
> > >> So i'm quite confident i'm reporting the right thing now :-)
> > >> If you would like me to run debug patches on top of this commit, don't 
> > >> hesitate to send them !
> > >> 
> > 
> > > Hmm.... I just looked at the commit, something that's obvious wrong is
> > > the use of gso_type to determine whether an extra slot is required,
> > > which is fixed by Annie yesterday. Annie fixed that for netback.c but
> > > missed interface.c.
> > 
> > > This can probably fix the problem you're seeing. I will submit a proper
> > > patch if you confirm that...
> > 
> > Although the patch seems correct in it's own right .. it doesn't seem to fix
> 
> I will submit that patch anyway...
> 
> > the issue when using 3.13.6 as a base and ..
> >   - pull all 3.14 patches from the  
> > git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git tree
> >   - apply paul's commit "ca2f09f2b2c6c25047cfc545d057c4edfcfe561c 
> > xen-netback: improve guest-receive-side flow control"
> >   - applying annie's v2 patch
> >   - applying your patch
> > as dom0 and using a 3.14-rc5 as domU kernel.
> > 
> > Unfortunately i'm still getting the Bad grant references ..
> > 
> 
> :-( That's bad news.
> 
> I guess you always have the same DomU kernel when testing? That means we

And apparently you're! Ignore this. I hit "send" too fast!

> can narrow down the bug to netback only.
> 
> Paul, do you have any idea what might go wrong?
> 
> Wei.

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