[CentOS] IOMMU and kernel

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