Update — 7+ days stable with retbleed=off Confirming that adding retbleed=off to boot parameters has completely resolved the crashes.
Current status: - Uptime: 7 days, 16 hours (and counting) - Kernel: 7.0.0-27-generic (Ubuntu 26.04 LTS) - CPU: AMD Ryzen 7 4800U (Zen2) - Zero crashes, zero dmesg errors related to srso/retbleed/rethunk Boot parameters that stabilized the system: processor.max_cstate=1 spec_rstack_overflow=off retbleed=off nmi_watchdog=1 Timeline of fixes attempted: 1. processor.max_cstate=1 alone → still crashed (srso_safe_ret) 2. Added spec_rstack_overflow=off → crash moved to retbleed_return_thunk 3. Added retbleed=off → stable since Jul 15 (7+ days, previously crashed every 12-36h) Conclusion: The return thunk mitigations (both SRSO and RETBleed) interact badly with cpuidle on Zen2 (Renoir/4800U), specifically in the swapper/0 → cpuidle_enter_state → sched_tick → timer interrupt path. Disabling both mitigations eliminates the crashes entirely. This is on a desktop/home-server workload (no VMs, no containers requiring mitigation isolation), so the security trade-off is acceptable for this user. However, the kernel should not crash regardless of mitigation state — this appears to be a code-generation or thunk- alignment bug in the mitigation implementation for this CPU family. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2160457 Title: Kernel panic in srso_safe_ret / kick_ilb during sched_tick on AMD Ryzen 7 4800U (Zen2) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2160457/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
