[PATCH 0/1][SRU][N][O][Unstable] Random flickering with Intel i915 (Comet Lake and Kaby Lake) on Linux 6.8+

[Agathe Porte]

2024-11-18 02:29 CET, AceLan Kao:
> From: "Chia-Lin Kao (AceLan)" <acelan.kao at canonical.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/2086587
> 
> [Impact]
> The flickering predominantly occurs when the mouse cursor is in the bottom
> quarter of the screen and stops when the cursor leaves this area.
> Extensive testing across various kernel versions revealed that the issue
> became apparent from kernel version 6.8.0 onward, correlating with the
> mentioned configuration changes, CONFIG_INTEL_IOMMU_DEFAULT_ON and
> CONFIG_INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON.
> The problem persists in the latest drm tip.
> 
> [Fix]
> As an immediate workaround, adding 'intel_iommu=igfx_off' to the kernel
> command line has been found to effectively eliminate the flickering issue.
> This patch proposes the same behavior as 'intel_iommu=igfx_off' and apply
> the rule to all Intel KBL and CML GPU IDs.
> 
> [Test]
> 1. Boot up to desktop with ubuntu kernels(6.8+)
> 2. Moving cursor around the desktop
> 3. There should be no flicker while cursor is moving
> 
> [Where problems could occur]
> For virtualized environments using hardware-assisted virtualization for
> graphics (such as VFIO or mediated pass-through), disabling IOMMU for
> graphics could either disable these features or reduce their security and
> efficiency.
> Usually, users pass the 'intel_iommu=on' by themselves when they are
> using related features. So, the impact of this change is minimal.
> 
> Chia-Lin Kao (AceLan) (1):
>   UBUNTU: SAUCE: iommu/intel: disable DMAR for KBL and CML integrated
>     gfx
> 
>  drivers/iommu/intel/iommu.c | 41 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)

Note that you tagged your SRU for Unstable, but I guess you meant plucky
instead?