[pve-devel] [PATCH docs 2/3] pci-passthrough: mention that `intel_iommu=on` is the default for 6.8+

[Christoph Heiss]

Thanks for taking a look!

On Tue, Oct 29, 2024 at 02:17:59PM GMT, Aaron Lauterer wrote:
> Looking at the surrounding context, I would rework this section even more.
> Before I just apply my approach, what do you think about the following
> change?
> ---
> diff --git a/qm-pci-passthrough.adoc b/qm-pci-passthrough.adoc
> index 4f19f2a..ca07692 100644
> --- a/qm-pci-passthrough.adoc
> +++ b/qm-pci-passthrough.adoc
> @@ -63,19 +63,18 @@ some configuration to enable PCI(e) passthrough.
>
>  .IOMMU
>
> -First, you will have to enable IOMMU support in your BIOS/UEFI. Usually the
> +You will have to enable IOMMU support in your BIOS/UEFI. Usually the
>  corresponding setting is called `IOMMU` or `VT-d`, but you should find the
> exact
>  option name in the manual of your motherboard.
>
> -For Intel CPUs, you also need to enable the IOMMU on the
> -xref:sysboot_edit_kernel_cmdline[kernel command line] kernels by adding:
> +With recent kernels (6.8 or newer), `IOMMU` should be enabled

I'd drop the code tags for IOMMU here (and add a "the") -- like in the
first sentence -- since this is referring to the IOMMU in a more general
sense rather than a specific setting as above such, IMO.

> automatically.

Since you drop the note about AMD CPUs below, I'd either keep that one
below or explicitly mention here that this automatic enablement is for
both Intel and AMD CPUs.

Otherwise users/admin might be left wondering what needs to be done for
AMD CPUs, if only Intel are mentioned here. Just to be thorough.

> +On older kernels, it was necessary to enable it on Intel CPUs via the
> +xref:sysboot_edit_kernel_cmdline[kernel command line] by adding:
>
>  ----
>   intel_iommu=on
>  ----
>
> -For AMD CPUs it should be enabled automatically.
> -
>  .IOMMU Passthrough Mode
>
>  If your hardware supports IOMMU passthrough mode, enabling this mode might
> [..]