Re: Need advice to develop some libxl patches

[Ian Campbell <Ian.Campbell@citrix.com>]

On Fri, 2013-02-08 at 11:36 +0000, Stefano Stabellini wrote:
> On Thu, 31 Jan 2013, Fabio Fantoni wrote:
> > I tested spice vdagent, spice audio and spice usbredirection with qemu
> > upstream and xen-unstable manually, is all working.
> > I'm start to write some patches to have all spice features on xen 4.3.
> > 
> > About vdagent probably no problem.
> > 
> > About spice audio on test I actually set this variable manually:
> > 
> > export QEMU_AUDIO_DRV=spice
> > 
> > I need know how to setup this env variable but for a given hvm domU start.
> > In other word I need to set this env variable on a per domU basis (if
> > spiceaudio if setted in cfg).
> 
> Pass it from libxl, after all QEMU is spawned by libxl

Setting envvars to configure qemu is a pretty crappy interface though,
given that qemu supports both command line and configuration files for
most other stuff. Perhaps this interface should be fixed upstream to use
the standard mechanisms first?

> > About usb redirection the qemu parameters to add are similar to this:
> > 
> > device_model_args=["-readconfig","/etc/xen/ich9-ehci-uhci.cfg","-chardev","spicevmc,name=usbredir,id=usbredirchardev1","-device","usb-redir,chardev=usbredirchardev1,id=usbredirdev1,bus=ehci.0,debug=3","-chardev","spicevmc,name=usbredir,id=usbredirchardev2","-device","usb-redir,chardev=usbredirchardev2,id=usbredirdev2,bus=ehci.0,debug=3","-chardev","spicevmc,name=usbredir,id=usbredirchardev3","-device","usb-redir,chardev=usbredirchardev3,id=usbredirdev3,bus=ehci.0,debug=3"]
> > 
> > Probably is not good point to external generic file (on my test
> > /etc/xen/ich9-ehci-uhci.cfg), someone can tell me the best way for do this?

What does /etc/xen/ich9-ehci-uhci.cfg contain? Perhaps we might want to
add USB passthrough as a concept in libxl so as to expose this in a more
"libxl" like manner, instead of just cutting through the qemu options?
(I think George also brought this up a while back).

Ian.