Re: [Xen-devel] [Xen-users] xen forum

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Wed, May 22, 2013 at 9:54 PM, Gordan Bobic <gordan@xxxxxxxxxx> wrote:
> OK, I can confirm that my VM configs start OK using xl. Unfortunately, xl in
> 4.2 doesn't support usb-add, so I cannot pass the required USB devices
> through, over and above the one I can pass in the config file.
>
> Will usb-add also be available in 4.3, in addition to the multi-device
> syntax in the config file?

Unfortunately not. :-(  I did start the process, but unfortunately
rather too late in the release cycle, and the design of a proper
interface took a lot longer than I expected.  The good news is that we
are in really good shape to have the feature in 4.4, which we're
expecting to be in 6 months (or less) from the release for 4.3.

If you're using this personally, and you're really keen, you could
apply the most recent patchset that I posted (or I could send you a
rebased version).  From a technical standpoint it's very
straightforward, and I had the basic functionality working months ago
for HVM domains with qemu-upstream.  So the patchset should work
fairly reliably; just be aware that the interface (both in xl and
libxl) may change before the final release.

> Any chance of the multi-device syntax also being patched into xm for 4.3?

I think at this point it's unlikely.  Even if we had the patches, it's
too late in the release process to risk introducing a bug to implement
this feature.

There is an all-purpose work-around, however.  Basically all of the
device options are parsed from the config file and then transmuted
into qemu command-line parameters.  There's a field in the config file
that allows you to pass in a string of options directly.  If you
wanted to add more usb devices, you can do something like this:

extra="-usbdevice $dev1 -usbdevice $dev2"

Where $dev1 and $dev2 are the same syntax you would use in the
"usbdevice" field of the config file.

This can be used to access other qemu features that are not
implemented by xm or xl as well.  It would all be "use at your own
risk", but there's no reason most of it shouldn't just work out of the
box.

 -George

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