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 02:00:41PM +0100, Sander Eikelenboom wrote:
[...]
> >> 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.
> 
> Yes my previous tests (from my previous mail):
> 
> - 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 "ca2f09f2b2c6c25047cfc545d057c4edfcfe561c xen-netback: improve guest-receive-side flow control".
> 
> Also seem to indicate just that, although it could also be something in this netback commit that triggers a latent bug in netfront, can't rule that one out completly.
> 
> But the trigger is in that commit &&
> annie's and your patch seem to have no effect at all( on this issue) &&
> later commits in 3.14 do seems to mask it / make it less likely to trigger, but do not fix it.
> 

Unfortunately I've stared at the same piece of code for some time but
don't have immediate clue. Later commits don't look suspecious either.

I also looked at netfront code, but there's no slot couting change
between 3.13 and 3.14.

Do you have some straight setup instructions so that I can try to
reproduce.

Wei.

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