Yes i can find intel_iommu=on. For some reason it doesnt take it when i reboot.

On Fri, 2020-04-03 at 18:44 +0200, Simon Matter via CentOS wrote:

...

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 you look at /boot/efi/EFI/centos/grub.cfg, do you see that the parameter has been added?

Regards, Simon

---

CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos

Yes

dmesg | grep "EFI v" [ 0.000000] efi: EFI v2.70 by American Megatrends

On Fri, 2020-04-03 at 14:29 -0400, Jonathan Billings wrote:

On Fri, Apr 03, 2020 at 07:37:10PM +0300, Georgios wrote:

...

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?

This is a libvirtd KVM machine? Are you sure you're using UEFI?

yes it exist.

thanks

On Fri, 2020-04-03 at 15:00 -0400, Jonathan Billings wrote:

On Fri, Apr 03, 2020 at 09:40:09PM +0300, Georgios wrote:

...

Yes

dmesg | grep "EFI v" [ 0.000000] efi: EFI v2.70 by American Megatrends

That's not always the best test, you should look for the existence of /sys/firmware/efi to determine if you're using an EFI system.

'grubby' knows to update the configuration file for Legacy vs. UEFI.

Hi,

I think i might have solve it.

For some reason grub2-mkconfig doesnt work. (Have no idea why)

Is this on CentOS 7?

Well, yes, I remember that it didn't work for me when I installed new servers one or two years ago, that was with CentOS 7 and they were my first EFI installs.

I manage to solve it with grubby.

sudo grubby --args="intel_iommu=on" --update-kernel=ALL

For some reason it works. I dont know if it works if my kernel gets upgraded.

I have restored the original configs after messing with grub2-mkconfig and only used kernel installs to further modify grub config. That way it has always worked for me. And I was a bis scared by the whole EFI, grub2 and everything around it because I felt I don't really understand how it all interacts in detail.

Regards, Simon