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Re: [Xen-devel] [PATCH V3 4/6] xl: add pvusb commands

On 05/21/2015 04:00 PM, George Dunlap wrote:
On 05/21/2015 02:55 PM, Juergen Gross wrote:
On 05/21/2015 03:43 PM, George Dunlap wrote:
On 05/21/2015 02:08 PM, Juergen Gross wrote:
On 05/21/2015 03:01 PM, George Dunlap wrote:
On 05/21/2015 12:58 PM, Juergen Gross wrote:
There might be existing users who know about "xm usb-assignable-list".

Yes -- unfortunately something has to give: either we confuse new users
with two names that sound similar but do something different, or we
confuse former xm users by renaming their function, or we confuse
current xl users by renaming their function.  There's badness to be had
whichever one we choose.  I think renaming the xm function is the least
bad of all the options.

OTOH I don't care giving it another name, as long as the functionality
is available.

OK -- what about "usb-available-list"?  Any objections / alternate
suggestions from anyone?

Hmm, just another idea:

xl usb-list -a

could list all domains with assigned USB-devices and the currently not
assigned devices as well. This would avoid the need for another command
name. It would even be possible to omit the "-a".

That works for me too, I guess.

Can I suggest, though, that work on that functionality be detached from
getting the core pvusb functionality in?  I can't really effectively do
the qemu side until it is in due to the cost of rebasing, and I would
really like to have both in for 4.6 if possible.


I hope to have my pvusb backend in qemu ready until then, too. :-)
In case the performance isn't too bad I'll have to make some changes to
the libxl part as well, but this will result in some deletions only
(qemu will do driver unbinding, this will no longer be required to be
done by libxl).

Right -- just like it's not necessary when qemu does emulated device
passthrough. :-)

Out of curiosity, what's the motivation for doing pvusb in qemu?  Will
there be an option, for instance, to switch usb devices from emulated
over to pv when the magic port is written to (as is done with disks &
network currently)?

Doing it in qemu was a request when I sent my patches to do it in the
kernel. :-)

Doing pvusb in qemu really has advantages. Just by using a newer Xen
you'll have pvusb backend support in Dom0. No need for a kernel update.

Up to now I have no plan doing a switch of emulated USB devices to pv.
TBH I don't think this is an important scenario. In case someone wants
to add support for it I won't object. :-)


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