Comment 13 for bug 1990985

Hi Kim,

Just like with Focal, for the Bionic backport of this fix, could you just
quickly confirm it's there and didn't break anything as you see it?

Thanks

On Tue, Nov 1, 2022 at 11:00 AM Ubuntu Kernel Bot <
<email address hidden>> wrote:

> This bug is awaiting verification that the linux/4.15.0-196.207 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-bionic' to 'verification-done-bionic'. If the
> problem still exists, change the tag 'verification-needed-bionic' to
> 'verification-failed-bionic'.
>
> 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!
>
> --
> You received this bug notification because you are a bug assignee.
> 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 Committed
> Status in linux source package in Focal:
> Fix Committed
> Status in linux source package in Jammy:
> Fix Committed
> Status in linux source package in Kinetic:
> In Progress
>
> 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 <email address hidden>
> Suggested-by: Rafael J. Wysocki <email address hidden>
> Signed-off-by: Dave Hansen <email address hidden>
> Reviewed-by: Mario Limonciello <email address hidden>
> Tested-by: K Prateek Nayak <email address hidden>
> Link:
> https://<email address hidden>/
> Link:
> https://<email address hidden>
>
> 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
>
> Launchpad-Notification-Type: bug
> Launchpad-Bug: distribution=ubuntu; sourcepackage=linux; component=main;
> status=In Progress; importance=Medium; <email address hidden>
> ;
> Launchpad-Bug: distribution=ubuntu; distroseries=bionic;
> sourcepackage=linux; component=main; status=Fix Committed;
> importance=Medium; <email address hidden>;
> Launchpad-Bug: distribution=ubuntu; distroseries=focal;
> sourcepackage=linux; component=main; status=Fix Committed;
> importance=Medium; <email address hidden>;
> Launchpad-Bug: distribution=ubuntu; distroseries=jammy;
> sourcepackage=linux; component=main; status=Fix Committed;
> importance=Medium; <email address hidden>;
> Launchpad-Bug: distribution=ubuntu; distroseries=kinetic;
> sourcepackage=linux; component=main; status=In Progress; importance=Medium;
> <email address hidden>;
> Launchpad-Bug-Tags: verification-done-focal verification-done-jammy
> Launchpad-Bug-Information-Type: Public
> Launchpad-Bug-Private: no
> Launchpad-Bug-Security-Vulnerability: no
> Launchpad-Bug-Commenters: bladernr kim-naru ubuntu-kernel-bot
> Launchpad-Bug-Reporter: Kim Naru (kim-naru)
> Launchpad-Bug-Modifier: Ubuntu Kernel Bot (ubuntu-kernel-bot)
> Launchpad-Message-Rationale: Assignee
> Launchpad-Message-For: bladernr
>
>

--
Jeff Lane
Engineering Manager
IHV/OEM Alliances and Server Certification

"Entropy isn't what it used to be."