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Bug#598057: our xen-netfront in featureset=xen kernels has smartpoll enabled, but probably shouldn't



Package: linux-image-2.6.32-5-xen-amd64
Version: 2.6.32-23

Hi,

I just witnessed a strange situation - a domU had its kernel updated from
2.6.32-4-amd64 to 2.6.32-bpo.5-xen-amd64, and all seemed well, but after
two hours it stopped responding on its (statically configured) eth0 device.

tcpdump of the bridge and the vif on the dom0 said that everything was all
right, the domU was making ARP requests for its gateway, and the gateway was
responding, but then the domU would just repeat the same request, over and
over again.

That sounded to me like a xen-netfront problem. I happen to watch xen.git,
so I know about this recent back-and-forth:

http://git.kernel.org/?p=linux/kernel/git/jeremy/xen.git;a=shortlog;h=refs/heads/xen/netfront

After September 10th this year, several bugs were identified in this new
smartpoll logic. I then checked in our package, and we seem to be using
an August 13th copy, so we're missing those.

I'm not at all sure that this was the issue in my problem, because I don't
completely grok all that stuff - I don't exactly know if xennet_interrupt()
or smart_poll_function() are what's getting stuck in my use case - but
debian/patches/features/all/xen/pvops.patch includes the smartpoll changes
and plain drivers/net/xen-netfront.c doesn't, and the latter has worked fine
for many months here while the former screwed us shortly after installation,
so that's suspicious enough for me.

Please update the kernel pvops patch to include the more recent xen/netfront
branch - where the benefit is both in that known smartpoll bugs are fixed,
and this new feature is turned off by default until upstream is more
comfortable with it. TIA.

-- 
     2. That which causes joy or happiness.



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