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 .
More info is available on this commit here: https://git.launchpad.net/~ubuntu- kernel/ubuntu/+source/linux/+git/unstable/commit/?id=14ebfcacaeb07b02235f2ea881fd6e34e3de0d6f 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 <philip....@canonical.com> > Acked-by: Andrei Gherzan <andrei.gher...@canonical.com> > Signed-off-by: Andrea Righi <andrea.ri...@canonical.com> 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. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/2062951 Title: Random flickering with Intel i915 (Gen9 GPUs) on Linux 6.8 (Ubuntu 24.04) Status in linux package in Ubuntu: Confirmed Bug description: After migrating Mantic 23.10 install to Linux 6.8.0, I am experiencing heavy flickering at random. It happens after a moderate to heavy on screen activity like window switching, scrolling etc. It never happens when playing video or when there is no interaction using keyboard/pointer. It tend to happen when the mouse cursor is in the bottom quarter of the screen and stops immediately when the cursor leaves that screen region. Around the same time the following appears in kernel log: kernel: i915 0000:00:02.0: [drm] *ERROR* CPU pipe A FIFO underrun Happens on both X11 and Wayland on both KDE plasma and Mate (though less). I first encountered the issue with Linux 6.8.0-11 and it still happens with Ubunutu's 6.8.0-28 and Mainline 6.8.7. Kernels 6.6, 6.5, 6.1 and older did not have that issue. Hardware is: Dell XPS 9350, Vendor Intel, Driver i915, Skylake GT2 [HD Graphics 520] Software: Ubuntu 23.10, KDE Plasma 5.27.10 / Mate 1.26 Attaching kernel log for 6.8.0-28 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2062951/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
