Re: [Xen-users] xl create argument issue with disk config

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Tue, 2015-11-17 at 00:42 -0600, Yaohua Li wrote:
> Thanks for the advice!
> 
> I can find the new device in xenstore-ls, but the OS code cannot read it
> out.

"xenstore-ls -fp" will give you the perms on the nodes, perhaps something
is wrong there?

>  Is it possible to *remove* some xenstore nodes, if the code is too
> wrong?

Do you mean is it possible for a buggy guest to remove a node by mistake?
There are wire protocol commands to remove nodes, and I think the guest
would have permissions to remove them, but it's not the sort of thing I
would expect a guest to be able to do by mistake.

> I can see that the new devices are created, from xenstore-ls.
> 
> Below is the output from one run of Ethos OS, with xl -vvv. It will crash
> and destroy the domain, so I won't see xenstore stuff afterwards.

If you "xl -vvv create -p" then it will create the guest paused, which will
give you a chance to inspect.

Have you tried a similar configuration using a known good OS (e.g. Linux or
FreeBSD perhaps)?

> libxl: verbose: libxl_create.c:130:libxl__domain_build_info_setdefault: 
> qemu-xen is unavailable, use qemu-xen-traditional instead: No such file or 
> directory

Ah, now this is interesting.

The use of a file: type device requires a qemu-xen process to provide the
backend, which it cannot find. There is a fallback to qemu-xen-traditional
(Xen's old fork of qemu) but it will not be well tested.

If you built from source you should have gotten a qemu-xen installed by
default unless you deliberately turned it off, if you got this from a
distro package then you may need to install it by hand (and maybe file a
wishlist bug with your distro to add a suitable dependency).

An alternative workaround would be to run losetup by hand on your disk
image and then tell the vm cfg to use phy:/dev/loopN.
[....]

> libxl_device.c:959:device_hotplug: calling hotplug script:
> /etc/xen/scripts/vif-ethos online

What does this script do which is different to the stock ones?

Ian.

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