Intel_iommu is set to on. Can I turn it off?

Software PureOS
1

Hello, I have a Librem Mini running PureOS with KDA Plasma. My technical knowledge is basic. I use the computer for basic everyday tasks. Looking at dmsg I see this line: [ 0.000000] Command line: root=UUID=4f51cc04-c4ad-42fb-a509-005ab7487791 ro i915.enable_rc6=0 quiet splash intel_iommu=on

What is IOMMU and can I set it to “off”? If so, how do I do that? From what I’ve read, its used for Virtual machines and I don’t need that.

Thanks in advance for your help!

2

Its seems like this is a booting and Kernel attribute, so you can clone some boot-setting with another entry (which you may be use by default) and just set this attribute to intel_iommu=off by just editing a string.

However, do you know what the IOMMU is?

It is (just) a directive to use direct Memory Access, with a Software Unit to save time and energy. If you disable it, you will loose more Energy by your Librem Mini, CPU for accessing Data in your Ram. I think this is not a big issue, you should use it. If you do not trust your Hardware… you should try to not store privacy information on it. I think IOMMU is fine. If you like not to share that data, try to just store and deliver encrypted data by your Librem Mini. This Way your Server just serve encrypted Data to your Clients (Smartphones, Notebooks, Desktop PCs, Ebooks, Screens with Raspberrypy etc…) to Display your Information in another way after encryption.

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3

Thanks so much for your reply! So I decided to turn Intel_iommu off. I updated grub and restarted however now I have both values “on” and “off” when I look at dmesg I see this:

[ 0.000000] Command line: root=UUID=4f51cc04-c4ad-42fb-a509-005ab7487790 ro intel_iommu=off intel_iommu=on vt.default_red=0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff

However in /etc/default/grub there is no value turning it on:
GRUB_DEFAULT=0
GRUB_HIDDEN_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR=lsb_release -i -s 2> /dev/null || echo Debian
GRUB_CMDLINE_LINUX_DEFAULT=“quiet splash”
GRUB_CMDLINE_LINUX=“i915.enable_rc6=0”
GRUB_CMDLINE_LINUX=“intel_iommu=off”

How do I know if the change took effect? If it is set to both “on” and “off”, which value will be ignored?

4

but only among other things. Unless you know what you are doing and have a compelling argument to turn it off … I would leave it on!

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