Re: [Xen-devel] Need advice to develop some libxl patches

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2013-02-08 at 15:13 +0000, Fabio Fantoni wrote:
> Il 08/02/2013 12:50, Ian Campbell ha scritto:
> > 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).
> 
> The content is here:
> http://xenbits.xen.org/gitweb/?p=qemu-upstream-unstable.git;a=blob_plain;f=docs/ich9-ehci-uhci.cfg;hb=HEAD
> 
> Spice usbredir redirects USB devices from client (where spice-client is 
> launched) to qemu, not from dom0 to qemu.
> How to expose it in a more "libxl" like manner?

Perhaps be defining a libxl_device_usb device type and including a list
of those in the domain config struct, like for other devices? We would
likely want to accommodate both emulated and passthrough devices.

Not sure how to handle USB topology though, if possible we should avoid
exposing this to the user and synthesise something suitable within
libxl.

Ian.


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