[Gllug] Xen hotplug problems (was Tornado in London)

[Daniel P. Berrange]

On Fri, Dec 08, 2006 at 04:20:42PM +0000, - Tethys wrote:
> On 12/8/06, Daniel P. Berrange <dan at berrange.com> wrote:
> 
> 
> >Ahh, the joy of Xen error reporting & its convoluted device architecture 
> >:-)
> 
> Indeed. For all I love Xen, and despite what Novell seem to believe,
> it *really* isn't ready for prime time use yet, for this very reason
> (and others, FWIW). It's fine when it works. But when it doesn't,
> you're on your own, due to the almost total absence of documentation.

Yeah, the number of data corruption issues/bugs I've encountered & fixed
in preparing Xen builds for Fedora/RHEL is really scary. Only last week I 
discovered the block device layer in Dom0 never reported any I/O errors 
back to the guest OS :-( It is getting better all the time, but there's
lots to do to bring it to the same quality as Linux baremetal & I certainly
don't envy Novell having to support the earlier version of Xen 3.0.2

> >Why run a shell script directly, when you can create a kernel module
> >which registers a sysfs file, which fires a notification to userspace,
> >which triggers udev, which runs a shell script.
> 
> Exactly.
> 
> >How many network cards does your host have & which is primary ? Also,
> >are you using the bridged networking config ?
> 
> 3 cards, eth0 is the primary (it's an e100 -- the other two are tg3).
> Yes, I'm using bridged networking, with the xend-config.sxp being
> identical to the one on my other working Xen machine (which has the
> same 3 cards, in the same order).

Hmm, damn, so eth0 is your primary nic - there goes my usual answer!
Basically network scripts are hardcode to bridge to xenbr0 unless
you specify an alternate bridge in the guest config file. If its a
paravirt guest, make sure the vif doesn't do not have 'type=ioemu',
conversely for fullvirt, make sure it /does/ have 'type=ioemu'.
Those are my two best answers to vif hotplug issues.

Dan.
-- 
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|=-   berrange at redhat.com  -  Daniel Berrange  -  dan at berrange.com    -=|
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