linux-kernel - thermal throttling on xps13: unchecked MSR access error

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Message-ID: <CAHk-=wgDEq2LYW6rnfQXmEOSfF8ECPkuwjJ3CR7aC4N2zuRLWQ@mail.gmail.com>
Date:   Tue, 13 Dec 2022 16:35:29 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Cc:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: thermal throttling on xps13: unchecked MSR access error

Hmm.

I don't think I've seen this before on my trusty old x86 laptop (XPS
13 9380 - it's a few years old)

    unchecked MSR access error: WRMSR to 0x1b1
      (tried to write 0x0000000004000aa8)
      at rIP: 0xffffffff8b8559fe (throttle_active_work+0xbe/0x1b0)

I'm blaming one of

  930d06bf071a ("thermal: intel: Protect clearing of thermal status bits")
  6fe1e64b6026 ("thermal: intel: Prevent accidental clearing of HFI status")

with no real reason apart from being the last commit to touch that
function, but also when it started happening.

The first kernel I see this for is 6.1.0-03225-g764822972d64, but
honestly, it's possible that it has happened before too, and the real
issue is that the machine just happened to be hot and throttling at
bootup and/or I just didn't notice.

The CPU in this thing is a

  Intel(R) Core(TM) i7-8565U CPU @ 1.80GHz

which hopefully makes somebody go "Ahh, yes, I missed that case".

I don't *think* the MSR access checking has changed, but maybe it did,
and I'm barking up the wrong tree.

Anybody?

                 Linus