Re: [Xen-users] PCI/VGA passthrough: differences between Xen and ESXi?

[Patrick Proniewski <patpro@xxxxxxxxxx>]

David, thanks for your answer, my remarks below:

On 02 avr. 2013, at 18:54, David TECHER wrote:

> Patrick,
> 
> 1) Xen's vocabulary 
> 
> dom0 = the main (first) hypervisor, hosting all virtual machines -- like your 
> Mac OS X
> domU = any virtual machine. 

ok, I've pretty much got that.


> My understanding is that your dom0 has to be replaced by Linux so you can run 
> Xen. But for this part I am not a Mac OS X expert.

Exactly. Bare metal would be nice, but ESXi is nothing more than a very slim 
linux, so a full linux+Xen is not a problem.


> 2) More info  - details listed beow are only available for a Xen dom0 running 
> on Linux.
> 
> [Extracted]:....I've ended my testing with ESXi, because I was not able to 
> passthrough sound device, and USB....
> [Comment]: With Xen you can :)

with VMWare you can too, but the hardware of the Mac Pro is not fully 
supported. It looks like a dedicated (PCI) sound card and USB controller would 
be easy to passthrough. 
Nonetheless, using ESXi it would probably require a dedicated card (sound and 
usb) for every VM I want passthrough in. That would make many cards.


> [Extracted]: ...with stock ATI Radeon..;
> [Comment]...Xen offers VGA PassThrough feature for ATI Radeon. 
> 
> Here is a link to a Youtube video to run Crysis 3 on a domU Windows 7 64 Bits 
> with HD 7970
> 
> http://www.youtube.com/watch?v=GTnchEG4YtI&feature=player_embedded

Nice, I've seen others and that's make me think of Xen as a possible solution. 
(abusé, le fond d'écran ;) )


> As you can see 
> 
> - I can use PCI Passthrough to add a XBOX 360 Paddle while playing Crysis 3 
> (see at 09:12 in the Video) 
> - I have sound too :)


Can you share USB between different VMs? I mean, usb port 1 to VM #1, usb port 
2 and 3 to VM #2...


> But it works on Linux domU too. Here is another Youtube video link
> 
> http://www.youtube.com/watch?feature=player_embedded&v=KzqOIMaBgX0
> 
> But you need to apply a few patches to able this feature with Xen 4.2 and 
> over. Not very complicated to do.
> Here are my instructions to do it but I know that there are currently better 
> way to test it
> 
> http://www.davidgis.fr/blog/index.php?2013/03/13/935-xen-43-vga-passthrough-ati-card-hd-7970-changeset-26706

Thanks. I'll take a look if I find a box do test.


> [Extracted]...memory allocation
> [Comment]...Xen - limited to 3GB for RAM. A few developers are working on 
> overpassing this limitation.

Oh my... Xen is dead to me. Seriously, I have 24 GB RAM, and use a big chunk of 
it, on my Mac active memory alone ranges from 6 to 11 GB, the remaining part is 
shared between inactive, and free.


> [Extracted]...no snaphost possible
> [Comment]...If you used Xen with LVM is then snahshotting is easier to manage 
> ;)

It would require either to snapshot every single VM, or to create a dedicated 
volume for each VM, not exactly what you get with ESX (snapshot per-VM 
independent of storage - even over NFS, including or excluding RAM). But well, 
a VM with passthrough in ESX as no snapshot capabilities, so relying on host FS 
is not a bad idea.


> [Extracted] no sleep
> [Comment] works on Xen for both Linux and Windows. The main issue is that you 
> can reboot a domU without restarting the dom0.

You've lost me here.


> [Extracted] Is it possible to create a virtualized desktop with VGA and PCI 
> passthrough for 2 or 3 VM's running simultaneously (ie. each one with its own 
> video card)?
> [Comment] Yes it is doable. Never tested but from experience share with other 
> Xen users  I know that it should be run fine.
> 
> Hope it helps.

It does, but I've to admit the RAM limit is a no-go for me (for now, I'll check 
facts in few months and follow the evolution on this topic).

Thanks,
Patrick


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