This bug is awaiting verification that the linux-lowlatency- hwe-5.19/5.19.0-1017.18~22.04.1 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-jammy' to 'verification-done-jammy'. If the problem still exists, change the tag 'verification-needed-jammy' to 'verification-failed-jammy'.
If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you! ** Tags added: kernel-spammed-jammy-linux-lowlatency-hwe-5.19 -- 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/1990985 Title: ACPI: processor idle: Practically limit "Dummy wait" workaround to old Intel systems Status in linux package in Ubuntu: In Progress Status in linux source package in Bionic: Fix Released Status in linux source package in Focal: Fix Released Status in linux source package in Jammy: Fix Released Status in linux source package in Kinetic: Fix Released Bug description: IMPACT: Old, circa 2002 chipsets have a bug: they don't go idle when they are supposed to. So, a workaround was added to slow the CPU down and ensure that the CPU waits a bit for the chipset to actually go idle. This workaround is ancient and has been in place in some form since the original kernel ACPI implementation. But, this workaround is very painful on modern systems. The "inl()" can take thousands of cycles (see Link: for some more detailed numbers and some fun kernel archaeology). First and foremost, modern systems should not be using this code. Typical Intel systems have not used it in over a decade because it is horribly inferior to MWAIT-based idle. Despite this, people do seem to be tripping over this workaround on AMD system today. Limit the "dummy wait" workaround to Intel systems. Keep Modern AMD systems from tripping over the workaround. Remotely modern Intel systems use intel_idle instead of this code and will, in practice, remain unaffected by the dummy wait. Reported-by: K Prateek Nayak <kprateek.na...@amd.com> Suggested-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com> Signed-off-by: Dave Hansen <dave.han...@linux.intel.com> Reviewed-by: Mario Limonciello <mario.limoncie...@amd.com> Tested-by: K Prateek Nayak <kprateek.na...@amd.com> Link: https://lore.kernel.org/all/20220921063638.2489-1-kprateek.na...@amd.com/ Link: https://lkml.kernel.org/r/20220922184745.3252932-1-dave.han...@intel.com FIX: This issue pertains to all Zen based processors starting with Naples(Zen1). All LTS releases will need this fix: https://github.com/torvalds/linux/commit/e400ad8b7e6a1b9102123c6240289a811501f7d9 TESTCASE: To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1990985/+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
