Update with more systematic reproduction and bisection data. Hardware confirmation (correcting/confirming the original report): - CPU: AMD Ryzen 5 7535U with Radeon Graphics - GPU: AMD Rembrandt [Radeon 680M] [1002:1681] — confirms the Rembrandt/ Radeon 680M identification in the original report is accurate. - BIOS: updated from 01.08.03 to W78 Ver. 01.09.00 (06/10/2026) since original report — issue persists unchanged on the new BIOS.
Kernel bisection (using locally available installed kernels, no external builds): - 7.0.0-22-generic: GOOD — confirmed reliably clean across multiple separate shutdown/reboot cycles, no kernel parameters or BIOS changes needed. - 7.0.0-29-generic: BAD — hangs with identical symptom. - 7.0.0-31-generic: BAD — hangs with identical symptom, reproduced repeatedly. => Regression window narrowed to somewhere between 7.0.0-22 and 7.0.0-29 (Ubuntu 26.04 HWE kernel point releases). Workarounds tested on the BAD kernel (7.0.0-31), none resolved the issue: - BIOS "Pre-boot DMA Protection" (AMD Rembrandt platform feature): disabled — no change. - Kernel parameter amd_iommu=off — no change (confirmed via dmesg/ /sys/kernel/iommu_groups that AMD-Vi was genuinely not initialized during the test, so this was a real test, not a no-op). - Kernel parameter pcie_aspm=off — no change. Symptom detail for clarity: after systemd completes the shutdown sequence cleanly (poweroff.target reached, systemd-journald stops logging as expected), the machine does not reach true ACPI S5. Symptoms observed post-"shutdown": power/status LED remains lit, and the keyboard backlight still visibly reacts to keypresses. This indicates the EC/keyboard controller domain remains active, not just a cosmetic LED issue. Only a ~10s hard power-button press fully cuts power. Left unattended overnight unplugged, this previously drained the battery completely; with kernel 7.0.0-22 the battery loss overnight was negligible (~2%), consistent with a genuine clean poweroff. Current mitigation: pinned to 7.0.0-22-generic via apt-mark hold pending a fix. Happy to test further bisection (7.0.0-23 through -28) from the Ubuntu archive if that would help narrow the regression commit range further — let me know if that's useful or if the 22/29 boundary is already enough to work with. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2163015 Title: System fails to power off / hangs on shutdown-reboot after upgrade to Kubuntu 26.04 (kernel 7.0) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2163015/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
