On 11/01/2024 17:00, Sean Christopherson wrote: > This is a known issue. It's mostly a KVM bug[1][2] (fix posted[3]), but I suspect > that a bug in the dynamic preemption model logic[4] is also contributing to the > behavior by causing KVM to yield on preempt models where it really shouldn't. Thanks a lot for the pointers and the proposed fixes! I still see the same temporary hangs with [3] applied on top of 6.7 (0dd3ee31). However, with [4] applied in addition, I have not seen any temporary hangs yet. As the v1 of [3] was reported to fix the reported bug [2] and looks very similar to the v2 I tried, I wonder whether I might be seeing a slightly different kind of hangs than the one reported in [2] -- also because the reproducer relies heavily on KSM and AFAICT, KSM was entirely disabled in [2]. I'll try to run a few more tests next week. FWIW, the kernel config relevant to preemption: CONFIG_PREEMPT_BUILD=y # CONFIG_PREEMPT_NONE is not set CONFIG_PREEMPT_VOLUNTARY=y # CONFIG_PREEMPT is not set CONFIG_PREEMPT_COUNT=y CONFIG_PREEMPTION=y CONFIG_PREEMPT_DYNAMIC=y CONFIG_PREEMPT_RCU=y CONFIG_HAVE_PREEMPT_DYNAMIC=y CONFIG_HAVE_PREEMPT_DYNAMIC_CALL=y CONFIG_PREEMPT_NOTIFIERS=y CONFIG_DRM_I915_PREEMPT_TIMEOUT=640 CONFIG_DRM_I915_PREEMPT_TIMEOUT_COMPUTE=7500 # CONFIG_DEBUG_PREEMPT is not set # CONFIG_PREEMPT_TRACER is not set # CONFIG_PREEMPTIRQ_DELAY_TEST is not set Thanks again! Friedrich > [1] https://lore.kernel.org/all/ZNnPF4W26ZbAyGto@xxxxxxxxxxxxxxxxxxxxxxxxx > [2] https://lore.kernel.org/all/bug-218259-28872@xxxxxxxxxxxxxxxxxxxxxxxxx%2F > [3] https://lore.kernel.org/all/20240110012045.505046-1-seanjc@xxxxxxxxxx > [4] https://lore.kernel.org/all/20240110214723.695930-1-seanjc@xxxxxxxxxx
