April 8, 20179 yr I have a GTX 770 passed through to a Windows 10 VM that causes the VM to perform worse than no GPU. It makes the VM behave like the refresh rate is about 10-15 fps. I have tried both OVMF and SeaBIOS. I am using the ACS override because there is a storage controller in the same IOMMU group as the GPU if I don't use the override. I have tried with Hyper-V on and off. Nothing seems to make a difference. The performance degradation is present from the moment the GPU is passed through, even before drivers are installed. What could be causing this? Thanks!
April 8, 20179 yr What slot on your motherboard is your GPU currently in? Do you have any other PCIe cards in your machine, if so what slots do they occupy?
April 8, 20179 yr Author Its in the 1st PCIe slot which is 16x. There is a SATA expansion card in the second full size 8x PCIe slot.
April 9, 20179 yr Some boards will drop the speed of the first PCIe slot to 8x if the second slot is occupied, just guessing here, but have you tried moving the SATA card to the next available PCIe slot and see if that makes a difference?
April 9, 20179 yr Author I will certainly try that, it just seems to me that 8x for operating just a windows desktop has always been more than enough.
May 9, 20179 yr do you have the rom file parameter in the VM? When I stopped specifying a external rom file for my 750Ti, my VM started performing like shit and weird stuff would happen (notification service didn't load, startup and shutdown times were a lot longer). When I put the line back in the XML, stuff went back to normal.
November 23, 20178 yr How are your IOMMU groups assigned? unRAID may have grouped your video card and sata card into the same IOMMU group which could cause resource issues.
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