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AMD AM4 platform poor OpenGL performance if IOMMU grouping is borked
The_Aquabat 24 Jul, 2019

Hi everyone.
Recently I had problems with HITMAN and Life is Strange, constant freezes, I just discovered that if I pass iommu=soft to grub, the bug is gone. I've been so much into vulkan gaming that I completely overlooked this, it happens only in OpenGL games. The problem is with some AM4 motherboards that have IOMMU broken, mostly the b350 but there are others.

you can check if you have this problem with this command

dmesg | grep AMD-Vi

if you read something about loop timed out or IO_PAGE_FAULT, then you probably have this problem.

MrNilsson 12 Aug, 2019

Mine looks like this:
GRUB_CMDLINE_LINUX="amd_iommu=on iommu=pt"

iommu=pt is using the passthrough mode and iommu=soft is using the software mode. You're only supposed to use one or the other, so don't put both in your grub file.

iwantlinuxgames 12 Aug, 2019

the Asrock Phantom Gaming 6 X399 motherboard also has this issue :/

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