Comment # 24 on bug 1229019 from Vasilis Liaskovitis

The good kernel 6.4.0-150600.23.14 log has this:

[    0.618918] pci 0000:00:1c.0: Intel PCH root port ACS workaround enabled
[    0.619153] pci 0000:00:1c.4: Intel PCH root port ACS workaround enabled

the bad one 6.4.0-150600.23.22 does not.

Did we remove a quirk for the Intel root device? I 'll investigate more.

For complete view of PCI on your system, could you also add output of:

lspci -vv

and maybe output from this script :

#!/bin/bash
for g in $(find /sys/kernel/iommu_groups/* -maxdepth 0 -type d | sort -V); do
    echo "IOMMU Group ${g##*/}:"
    for d in $g/devices/*; do
        echo -e "\t$(lspci -nns ${d##*/})"
    done;
done;


from both the good and bad kernel (all as root).