[CentOS] IOMMU and kernel

Fri Apr 3 16:37:10 UTC 2020
Georgios <gpdsbe+centos at mailbox.org>

Hi.
Im trying to set intel_iommu=on on kernel parameters at grub but for
some reason it doesnt work.

I edit /etc/default/grub file and i add the parameter.

then i run grub2-mkconfig -o /boot/efi/EFI/centos/grub.cfg and then i
reboot.

when i run virt-host-validate i get 

QEMU: Checking if IOMMU is enabled by kernel: WARN (IOMMU appears to be
disabled in kernel. Add intel_iommu=on to kernel cmdline arguments)

when i edit the grub menu durring boot and i put intel_iommu=on and the
i run again virt-host-validate i get

QEMU: Checking if IOMMU is enabled by kernel: PASS


any ideas?

I tried editing other variables like GRUB_TIMEOUT and it seems to me
that changes are applied.

Thanks in advance