Re: [Xen-users] use PCI VGA card on domU, and questions about USB

["Nick Couchman" <Nick.Couchman@xxxxxxxxx>]

>>> On 2010/06/25 at 10:59, Doublehp <doublehp-xen@xxxxxxxxxxxx> wrote: 
> Hello.
> 
> I have several video cards and want to use one of them for a particular domU
> 
> http://wiki.xensource.com/xenwiki/XenFaq section 7.3 states "not at the
> moment"; but, i know that this have been written years ago, and that
> since that time, things changed.
> 
> I found last month a page telling how to pactch a kernel, but, i can't
> find it again.
> 
> Can you point me to the right "up to date" page, or mailing list archive ?

If you're talking about passing through a graphics card to a domU, yes, this 
works now, with a few conditions.  First, I believe it only works on HVM domUs 
at the moment.  Also, the list of cards is fairly limited - there are some more 
patches making their way through development to make other cards work.  
Finally, this only works in Xen 4 - you must update to Xen 4 in order to use 
VGA pass through.  If you look at the Wiki you referenced above, you can find 
some other pages specifically about VGA pass through.

> 
> ATM I am using ATI R4350 on AMD 64, Gentoo stable, with kernel XEN
> 2.6.34 (xen-source).
> 
> For now, what I want to know is:
> - what are the patches required to use PCI devices under domU (VGA for
> now, but maybe other ones later on)
> - are those patches included automaticly by the gentoo package xen-source ?
> - what are the symboles i must activate ?
> - boot arguments to add
> - HVM conf to customise
> 
> But all of this may be explained in a forum or Wiki. I just don't find it.

http://wiki.xensource.com/xenwiki/XenPCIpassthrough

http://wiki.xensource.com/xenwiki/XenVGAPassthrough

> 
> Does Qemu support PCI hotplug ? to add PCI card after boot like for USB:
> usb_add host:xxxx:yyyy

Yes, I believe it does.  Don't remember the commands off the top of my head.

> 
> *** *** ***
> 
> I have a related problem:
> let say i want to plug a specific USB device to domU before i start the
> machine; then i put in the conf:
> 
> usbdevice = "host:0421:04f0"
> 
> This works fine. When starting the domU, it works as expected. But, the
> mouse in VNC goes wrong. The mouse normally get fixed with
> usb=1
> usbdevice='tablet'
> 
> but as I add usbdevice = "host:0421:04f0", usbdevice='tablet' seems
> ignored. What's wrong ? maybe i should do something like
> usbdevice={'tablet', "host:0421:04f0"} ?

Many versions of Xen are limited to a single USB device being passed through to 
the domU.  Version 4.0 may be the first version that does not have this 
limitation.  Since the tablet is considered a USB device, you have to choose - 
tablet (absolute mouse) support, or USB support - you can't have both (at least 
in versions of Xen prior to 4).  Even in the versions that do support multiple 
USB devices, you sometimes have to add the secondary ones after boot time.

-Nick

> 
> Is it possible to dedicate to a domU a specific USB branch ? I mean, a
> port on the dom0, or a Hub, so that, i just put this node/plug in the
> HVM conf, and, all peripherals i add after starting domU will be managed
> by the domU automaticly.
> 
> Is it possible to add a USB device to a domU/Qemu from a domO console ?
> I mean, run a bash command or script, instead of having to hit
> ctrl-alt-2 in the vnc/qemu window.
> 
> I will have the problem again if I want to add several PCI devices to my
> domU:
> pci=['02:00.0','02:00.1','03:00.0','03:00.1']
> ?
> 
> Thanks.



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