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

[Wei Liu <wei.liu2@citrix.com>]

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
can narrow down the bug to netback only.

Paul, do you have any idea what might go wrong?

Wei.