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

[Chia-Lin Kao (AceLan)]

On Tue, Nov 19, 2024 at 04:48:51PM +0100, Agathe Porte wrote:
> 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?
Correct, I just want this SAUCE patch could be preserved in the future
kernels.