Missing iomu (IOMMU) items (kernel support and drivers)

Currently whenever you download the current official release build of the Generic PC build of LibreELEC there isn't any IOMMU support. Without this support there are motherboards which won't be able to boot from USB Flash Drives or use external SD card readers that operate from USB. In the current situation with the official installation and update images it doesn't matter if IOMMU support is switched on or off in the BIOS (or UEFI); as well as the CPU supporting it.

It is due to there being a three part approach to IOMMU support:-

1. The Central Processor (CPU) needs to have the manufacturers technology for it (e.g. AMD IOMMU or Intel VT-d)
2. The Motherboard (Mainboard) needs to have support for said technology
3. The Operating System Software (OS) needs to have support for said technology (e.g. LibreELEC or other GNU/Linux distributions)

All attempts to do so result in a mount error and booting then grinds to a complete halt. Due to the BIOS only allowing for and expecting GNU/Linux virtualisation guests and not it being the primary and only OS. Preventing access to USB and several other similar ports from the operating system software without it present.

For more information on which items of hardware support the IOMMU technology (generally but may not be affected), see this website: List of IOMMU-supporting hardware - Wikipedia.

It can only be worked around (or fixed) by including support for IOMMU in the installation and update images and having that support switched on in BIOS (or UEFI) going forward. Just enough support for IOMMU to enable the system to boot successfully around the issue but not be a host or source of virtualisation. As this is a Just enough Operating System for Kodi in essence a handmade set top box appliance (or other appliance type device).

This problem is present on the following motherboards with (or without) the IOMMU support switched on:-

Motherboard

• Gigabyte GA-970A-DS3P v2.0 with AMD IOMMU (state independent - on and off)

Central Processor Unit (CPU)

• AMD FX 8350

If you know of other motherboards and central processor units which has these problems, please comment the appropriate information about the CPU and motherboard in a post below.

Affected LibreELEC versions:- Official installation/update images versions 8.2.4 or below without IOMMU support

Unaffected LibreELEC versions:- Custom builds with IOMMU support

I have submitted a pull request.

Updated options - to add support for iOMMU by MrGrymReaper · Pull Request #2602 · LibreELEC/LibreELEC.tv · GitHub

No virtualisation. Bare metal but AMD IOMMU support needs to be active in order to enable the ability to boot successfully.

When the IOMMU support chain is broken as mentioned in the original post. The USB ports gets cut off (becomes inaccessible) around after the Boot loader has done its work and is trying to start the scripts, but is fine up to that point.

This includes keyboard, mice, external card readers and USB flash drivers which use the port and other USB connected devices.

When it comes to mounting the next stage of the installation media it runs into a mount error, as it is unable to find the USB Flash drive in the port.

Also the USB Flash Drive is completely ok as it is a new drive and the image has been CRC checked.

milhouse - vpeter (on #librelec freenode.net) custom created the image file for me from during Yesterday evening or night. It took 15 hours for the image to build then he uploaded it for me today. I downloaded the image and tested the booting on said system and it booted ok.

In fact it got to the menu where you can choose to install, view install log or reboot.

He may have a copy of the kernel config file.

milhouse - I tried that in the past before getting that custom built image. That option didn't help one bit as the support wasn't built into the kernel, as part of the image.

Enabling iommu=soft all I got for the setting was the same result as in original post.

The custom image with the IOMMU support allowed the boot to proceed with out setting that option.

Setting that option with iommu support included just makes quiet (hides a wall of messages about AMD IOMMU). While keeping the IOMMU support active and working.

These two lines were mentioned for the appropriate kernel configuration file:-

CONFIG_IOMMU_SUPPORT=yes

CONFIG_AMD_IOMMU=yes

He also added the IOMMU drivers as well to the kernel used on the custom image.

1fichier.com: Cloud Storage

Any future update or installation images which removes or replaces a kernel with these set for the image will return to original post issue. Resulting in an inability to successfully boot the LibreELEC on affected systems.

My motherboard is Gigabyte GA-970A-DS3P v2.x using the latest released bios version FD. And they give me the run around I reported to them the issue revolving around Meltdown and Spectre vulnerabilities. Asked for a BIOS update for the motherboard seeing as the processor is affected.

That was back during January 2018 and we are now over half way through March 2018 (19 March 2018). With still no update for the BIOS or any press releases about an update incoming.