GPU in IOMMU group with PCI bridge


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Hi,

 

I'm trying to setup GPU passthrough for a Windows 10 VM and have a question about my IOMMU grouping.

 

Hardware

M/B: Supermicro - X11SSM-F
CPU: Intel® Xeon® CPU E3-1230 v6 @ 3.50GHz
HVM: Enabled
IOMMU: Enabled
GPU: MSi GeForce GT 710

The relevant IOMMU group shows:

IOMMU group 1:	[8086:1901] 00:01.0 PCI bridge: Intel Corporation Xeon E3-1200 v5/E3-1500 v5/6th Gen Core Processor PCIe Controller (x16) (rev 05)
		[10de:128b] 01:00.0 VGA compatible controller: NVIDIA Corporation GK208B [GeForce GT 710] (rev a1)
		[10de:0e0f] 01:00.1 Audio device: NVIDIA Corporation GK208 HDMI/DP Audio Controller (rev a1)

Everything I have read says that the GPU must be in its own IOMMU group for passthrough to work. However my Windows 10 VM seems to be working fine with the GPU and audio portion passed through even though there is a PCI bridge in the same group.

 

The VM boots up, there are no issues with the image and I don't see any errors in my logs. The monitor doesn't go to sleep unexpectedly and I can reboot and power off and restart the VM consistently. My question is, can the fact that the PCI bridge is in the same IOMMU group be causing any problems that aren't immediately apparent and will cause me grief down the road? I know I can enable PCIe ACS override to force my GPU into its own group as I have tried it and it works but I'm not comfortable with the warning that data corruption may occur. I built this primarily as a media server and the Windows 10 VM was a secondary thought after the fact. I realized that I had horsepower to spare and figured I could replace my aging Core 2 desktop with it. If it's going to cause me any problems though I would prefer to just pull the GPU and continue to RDP into the VM.

 

Would a different GPU behave differently and possibly go into its own IOMMU group? I purchased the GT 710 specifically for this as I don't game and it was fairly cheap but if I have to return it and buy something else that is know to work easily I could do that.

 

Thanks for any input.

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  • 2 weeks later...

Thanks for the reply. I appreciate it.

 

I decided to go ahead and order a GT730 that plugs into one of the x4 (in x8) slots. There are two of those slots on my motherboard and anything plugged into them goes into its own IOMMU group.

 

As I mentioned I don't game and just needed something to give me an image on the screen so this solution worked out perfectly for me.

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You can do so much research and still run into these integration issues when you build out. That is why I like to buy stuff from a place that accepts returns (Amazon has served me well in this regard).

I bought a $650 Quadro M4000 on Craigslist for my build and it turns out that I didn't need to do that at all. My $180 GPU would have worked fine, and I could have just added a second one for less money. Oh well... sometimes I miss experimenting with OPM (other people's money).

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I thought I did a lot of research before I got all the parts for my build but like you say sometimes issues don't become apparent until you've actually finished the build. I didn't even realize that GPU passthrough was something I would want to do, to be honest, so I guess I'm lucky that I was able to resolve the issue. Lucky too that since the GPUs I ended up getting are fairly old, Amazon was the only place I could find them so returning the first one wasn't a problem.

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  • 1 year later...

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