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

[Patrick Proniewski <patpro@xxxxxxxxxx>]

Hi Casey,

On 04 avr. 2013, at 18:43, Casey DeLorme wrote:

> I have shared the same card by shutting down one instance and booting 
> another, but there is a performance degradation problem which I would say is 
> due to the lack of FLR in consumer graphics cards.  There are work-arounds 
> but they will feel "hacky", just be ready to deal with major pains getting 
> multiple machines using the same card and make plenty of backups.  I don't 
> know how ESXi handles this problem, but if you do I would love to know more.

As far as I remember (my tests are few months old), as soon as you passthrough 
a PCI device into an ESXi VM, it's flagged into ESXi as no longer available, so 
you can't create another VM using the same device, even if the first one is 
shutdown.
The deal is probably very different with special device like Nvidia's VGX K2, 
but I don't think it's real passthrough, it's more likely delegation of GPU 
power.


> I use a macbook so I know where you are coming from, I totally prefer the 
> mac/unix environment for a workstation.  Unfortunately I am pretty sure that 
> OS X requires a UEFI bootloader, and that only exists in upstream-qemu which 
> to my knowledge does not yet work with VGA Passthrough.  You would be stuck 
> in SDL or VNC, or maybe ssh, not that those are necessarily bad. 

You can do GPU passthrough in a virtualized Mac OS X on top of ESXi pretty 
easily. The only limitation ("legal", not technical), is to run this VM on top 
of a supported Mac (Mac Pro or XServe - haha.). Many users have successfully 
ran Mac OS X VMs on ESXi on top of Mac Mini or other Macs.

I've made some benches: 
<http://www.patpro.net/blog/index.php/2012/12/15/2292-mac-os-x-benchmark-native-vs-virtualized-part-2/>
<http://www.patpro.net/blog/index.php/2012/12/17/2342-benchmark-virtualized-os-x-vs-windows/>

Now, if I switch to non-Apple hardware, I'll enter the world of hackintosh. 
Many users are running Mac OS X on non-Apple hardware, some are running Mac OS 
X VMs on top of VMware products, and I've even found some example of users 
running an "hackitoshed" Mac OS X on top of Xen with or without VGA passthrough.


> Good luck with your adventures,

thanks!

Patrick
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