Dear all,

Vt-d seems to be broken since I upgraded to kernel 5.5, there is a new
dmesg that was not there in 5.4:
"DMAR: [Firmware Bug]: No firmware reserved region can cover this RMRR
[0x0000000041d92000-0x0000000041d94fff], contact BIOS vendor for fixes"

System motherboard is Asrock X299 Taichi XE, bios 1.70, CPU is Core i9 7920
Vt-d and gpu passthrough was working ok since kernel 4.20 when I purchased
it

I attached the dmesg I get with kernel 5.5.1, and the dmesg from 5.4.17.

Also, I use the following script that displays the IOMMU groups, I found
the script there
https://wiki.archlinux.org/index.php/PCI_passthrough_via_OVMF

#!/bin/bash
shopt -s nullglob
for d in /sys/kernel/iommu_groups/*/devices/*; do
    n=${d#*/iommu_groups/*}; n=${n%%/*}
    printf 'IOMMU Group %s ' "$n"
    lspci -nns "${d##*/}"
done;

The output of this script with kernel 5.4.17 is attached to this email.
The same script with kernel 5.5.1 produces an empty output

Hope it helps narrowing down the problem, please ask additional info if
needed. Sorry if this is not submitted as it should be (then please
advise), first time I report -what apprears to be- a bug.

Best,
Thomas