Re: [Xen-users] Error with 5+ network interfaces

[Nate Soule <nsoule@xxxxxxx>]

Thanks very much for the background and your help Ian. Moving to PV NICs 
may well be fine in our situation. I have not yet tested that, but 
adding device_model_version="qemu-xen-traditional" to my configuration 
did the trick as well.
Thanks again, this was a huge help!

-Nate

On 05/08/2015 05:34 AM, Ian Campbell wrote:
> On Thu, 2015-05-07 at 15:11 -0400, Nate Soule wrote:
> > I posted this question on the Xen general form, but got the advice
> > that this was a complex enough issue that this mailing list may be the
> > better venue. Any advice would be greatly appreciated. See original
> > posting below.
> > Thanks.
> > -Nate
> > ---------------------------------------------------------
> > Hi, I'm attempting to create/start a guest VM with 5 network
> > interfaces (all bridges, specified in vif= line in config file, see
> > below). With 1, 2, 3, and 4 interfaces defined the VM starts perfectly
> > fine. With 5 or more interfaces defined I get the following errors
> > upon executing "sudo xl create SWITCH.cfg"
> >
> > Parsing config from SWITCH.cfg
> > libxl: error: libxl_dm.c:1388:device_model_spawn_outcome: domain 16
> > device model: spawn failed (rc=-3)
> > libxl: error: libxl_create.c:1186:domcreate_devmodel_started: device
> > model did not start: -3
> > libxl: error: libxl_dm.c:1492:kill_device_model: Device Model already
> > exited
> >
> > and the VM does not start.
> >
> > Is there any known limitation on number of network interfaces?
> >
> > Both dom0 and the domU are Ubuntu 14.04 (server edition). I have
> > replicated this on two separate physical machines (one with 8 GB RAM,
> > the other with 32 GB, in case it's relevant). I'm using Xen 4.4.1.
> I believe this bug was fixed in Xen 4.5. It's to do with the amount of
> memory used by the option roms for each emulated NIC, if you have too
> many it exhausts the slack space set aside for such things.
>
> If you have PV drivers in the guest then you could try specifying
> type=vif for one or more of the devices to force them to PV only mode
> such that you only have <=4 emulated NICs. Using PV is good practice
> anyway since it will perform much better.
>
> If you really need emulated NICs for some reason then I'm not sure if
> there is a workaround in 4.4 but you could try seeing if there is some
> backdoor way to disable that (perhaps using the device_model_args option
> in the cfg file to pass extra stuff to qemu).
>
> > I tried on a 3rd machine running Xen 4.1.6.1 and I do not appear to
> > get the issue there.
> 4.1 used an older qemu by default which didn't suffer from this sort of
> thing, it's only the upstream version of qemu which has it (due to
> changes in the way modern qemu accounts for memory etc).
>
> Which suggests that device_model_version="qemu-xen-traditional" in your
> config might also suffice as a workaround on 4.4.
>
> Ian.
>
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxx
> http://lists.xen.org/xen-users

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxx
http://lists.xen.org/xen-users