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Does PCI-passthrough work for pcie Soundcard and VGA?

Posted: 16. Jul 2011, 20:36
by sonnet
As per title I wanted to ask if pci passthrough new feature on virtualbox 4.1 beta works for pci-express soundcard and VGA.
If yes, is there much loss in latency (for soundcards) or drop in performance?

Re: Does PCI-passthrough work for pcie Soundcard and VGA?

Posted: 16. Jul 2011, 22:12
by Sasquatch
Moved to beta, as the question is about a beta release.

Re: Does PCI-passthrough work for pcie Soundcard and VGA?

Posted: 17. Jul 2011, 14:22
by Technologov
pci-express VGA - no.

docs say: "9.6. PCI passthrough"

"AGP and certain PCI Express cards are not supported at the moment if they rely on GART (Graphics Address Remapping Table) unit programming for texture management as it does rather nontrivial operations with pages remapping interfering with IOMMU. This limitation may be lifted in future releases."

Re: Does PCI-passthrough work for pcie Soundcard and VGA?

Posted: 17. Jul 2011, 15:09
by sonnet
so it works for pci-express soundcard I assume?

Re: Does PCI-passthrough work for pcie Soundcard and VGA?

Posted: 17. Jul 2011, 15:55
by levk
I tried to google stuff on the GART sentence and, as far as I understand, it doesn't necessarily mean video cards in general won't work. It isn't clear for sure and I can't test it because PCI passthrough doesn't seem to work at all for me on a Q45 chipset http://forums.virtualbox.org/viewtopic.php?f=15&t=43012

Re: Does PCI-passthrough work for pcie Soundcard and VGA?

Posted: 17. Jul 2011, 19:37
by Technologov
Unfortunately the whole PCI-passthrough topic is pretty theoretical, until Intel starts to offer such (VT-d) hardware.

The fact is -- my brand new High-end PC (XRig 2011) for $3000+ with Intel Core i7 2600K CPU _doesn't_ support VT-d.
Other solutions are either much slower (AMD, or Intel i7 2600 non-K, or prohibitively expensive - i7 980X)

Intel is to blame.

-Technologov

Re: Does PCI-passthrough work for pcie Soundcard and VGA?

Posted: 17. Jul 2011, 21:31
by Zrax
It depends a lot on what CPU and motherboard you have... My system is a little over a year old, but does have VT-d support which I had to enable in the BIOS, separately from the VT-x support. For reference, I have a Core i7 Bloomfield running on an Asus board with the X58 chipset; it's high-end, but certainly not in the "prohibitively expensive" range...

Unfortunately, my only PCI/PCI-e card is my video card, so I can't really test this feature quite yet... But still, sounds pretty neat :)

Re: Does PCI-passthrough work for pcie Soundcard and VGA?

Posted: 18. Jul 2011, 00:49
by kngtrider
Although correct in citing that VT-d is a relatively uncommon feature to say VT-x, do note that for intels K unlocked SKUs of sandy bridge, vt-d and other features such as TXT are disabled, but these features are enabled on the locked/cheaper SKUs

http://ark.intel.com/compare/52209,52210,52213,52214

intel figured the typical buyer of the unlocked parts would be an enthusiast who would overclock (purpose of buying the unlock to begin with) and not a pro/developer/business customer and to acheive good yields of parts that acheive high bins that can be sold and branded as unlocked parts disabled certain features to acheive this goal. wether those features where suspectible to failure on the wafers or that they just dont allow for headroom I do not know.

So its slightly incorrect saying 'my $3000 rig with 2600K does not support VT-d' when one did not specifically check if said feature is supported on a platform, not much different to in prior times where one was building a virtualisation host and certain newer intel cpus did not have vt-x while older ones did.

Regards

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