I'm having trouble enabling IOMMU on Centos 8 (4.18.0-147.8.1.el8_1.x86_64) and I'm starting to think that my CPU doesn't support VT-d.
On the Intel ARK page for my CPU it says "yes" for VT-x and VT-d but there is also the following sentence:
This product includes VT-d support only on the C2 stepping. Stepping information can be viewed via the menu on the left.
I have no idea what the "menu on the left" is" but if I look for the stepping of my CPU I get the following:
$ cat /proc/cpuinfo | grep stepping stepping : 7
Does "stepping 7" comes before or after "stepping C2"?
I have the following UEFI settings:
- Intel Virtualization Technology: Enabled
- Intel(R) I/OAT: Disabled
- Intel(R) VT-d: Enabled
- and everything else enabled (except Limit CPUID Maximum which is Disabled)
To check if IOMMU is enabled I tried:
$ dmesg | grep -E "DMAR|IOMMU"
ARN (IOMMU appears to be disabled in kernel. Add intel_iommu=on to kernel cmdline arguments)
Settings I tried to append to GRUB_CMDLINE_LINUX in
intel_iommu=on iommu=pt iommu=1
Then apply the changes to grub with:
$ sudo grub2-mkconfig -o /boot/grub2/grub.cfg
$ sudo dracut --regenerate-all --force