Comment 48 for bug 2062951

Despite some of the nondeterminism behind this bug, I believe I have bisected this bug to the following commit in the Ubuntu kernel tree: 14ebfcacaeb07b02235f2ea881fd6e34e3de0d6f (edit: I meant to refer to the corresponding commit in the noble kernel: 77e530c1a864c601b96622db03bc1f38e51155f1 ).

More info is available on this commit here: https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/unstable/commit/?id=14ebfcacaeb07b02235f2ea881fd6e34e3de0d6f (edit: I meant to link to the corresponding commit in the noble kernel: https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/noble/commit/?id=77e530c1a864c601b96622db03bc1f38e51155f1 )

The commit text reads:

> UBUNTU: [Config] enable Intel DMA remapping by default
> BugLink: https://bugs.launchpad.net/bugs/1951440
>
> We have tried in the past to enable CONFIG_INTEL_IOMMU_DEFAULT_ON and
> CONFIG_INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON (starting with Jammy), but
> there were multiple issues (especially with old hardware), so we ended
> up disabling these options afterwards, see LP: #1971699.
>
> Considering that IOMMU is enabled by default in upstream kernels,
> probably most of these issues are solved now (or old hardware has been
> decommissioned).
>
> Moreover, having this enabled by default can prevent potential issues
> with modern hardware and drivers (see for example LP #1958004).
>
> Acked-by: Philip Cox <email address hidden>
> Acked-by: Andrei Gherzan <email address hidden>
> Signed-off-by: Andrea Righi <email address hidden>

The commit text even predicts that the commit may introduce problems with older hardware. Its predictions appear unfortunately accurate.

Operating under the assumption that this commit introduced the bug, as a workaround, I have found that adding:

intel_iommu=igfx_off

to the GRUB_CMDLINE appears to resolve the issue for me.

Unfortunately, there appears to be no relief in the newest kernels. I tried the latest daily build available here: https://kernel.ubuntu.com/mainline/daily/

...and found that the issue still persists there with the default GRUB_CMDLINE.