Without actually reading current kernel source code, I have found on the
web:
iommu=soft. It deactivates the hardware IOMMU (which causes numerous DMA
errors on my system) and uses a software IOMMU instead.
A colleague had to use iommu=soft with a UEFI enabled linux on a
motherboard that did not have SecureBoot enabled in order for the UEFI
enable linux to work with the USB 2 port. Evidently, USB 2 is not
regarded as UEFI "secure" and has to enabled/used in a particular method
for a USB 2 port to be usable on a UEFI machine. USB 3 works fine.
However, the software IOMMU evidently runs noticeable "slower" than the
hardware IOMMU (that does not function). Has anyone experienced this
issue and does anyone have a suggested workaround?
Yasha Karant
