AMD IOMMU Driver Reworked For Linux 5.5

[phoronix]

Phoronix: AMD IOMMU Driver Reworked For Linux 5.5

With the IOMMU updates for the Linux 5.5 kernel there is a major rework to the AMD IOMMU driver to make use of more common DMA IOMMU code for implementing the DMA API but with an admitted risk of potential new regressions...

http://www.phoronix.com/scan.php?page=news_item&px=AMD-IOMMU-Linux-5.5

[dc740]

well... I had to disable it to get an stable system on my GA-AX370 Gaming K7 mobo. Audio playback had random noises when IOMMU was enabled, and I kept getting messages in my system logs... I can't remember all symptoms cause it was a long time ago, and I simply disable it after each bios upgrade now, but it was baaad. Getting a complete rewrite at least gives it a chance to actually work.

[muncrief]

Oh sheesh, that's a bit worrying and makes me want to compile it to check out my Windows 10 KVM with GPU passthrough. I'm trying to hold off at least until the merge window closes though. But I don't know now ...

UPDATE:
I couldn't help it so I compiled the master git and tested my VM and the GPU, USB, and SATA passthrough still seem to work perfectly. It even seemed a bit snappier, though that's purely anecdotal. Unfortunately the new NVME sensor doesn't work anymore, even though I checked and the patch is indeed in master, so I cut the rest of my testing short and went back to my custom compiled 5.4 with the manual NVME patch applied.

By the way I'm running a Ryzen R7 3700x on an ASUS TUF X570-PLUS MB that gives the Windows 10 VM a GT 710 GPU, VIA USB 3.0 board, and VIA SATA board. Yeah, that's right, I gave W10 all the cheap stuff

[Mangix]

I reported a bug with the mt7612u driver, which was not working properly on AMD hardware. This led to an alignment bugfix for the AMD IOMMU driver. Hopefully this rework fixes a class of bugs.