[arch-general] General protections faults / kernel panics with the Apple Magic Trackpad 2

[Merlin Büge]

Just for the record, someone else was debugging this a few days later:
https://bugzilla.kernel.org/show_bug.cgi?id=210241

And proposed a patch, which fixes the issue for both them and me:
https://patchwork.kernel.org/project/linux-input/patch/20201119082232.8774-1-felixhaedicke@web.de/

Regards,

Merlin


On Fri, 6 Nov 2020 06:08:09 +0100, Merlin Büge wrote:

> Hi all.
> 
> I think I need some help with debugging an issue I have.
> 
> I recently bought an "Apple Magic Trackpad 2" for reducing strain on my
> hand (since I have some RSI[0] issues currently), which is supported in
> Linux since version 4.20[1].
> 
> After connecting it to my laptop it worked instantly at first, but
> "sometimes" un- and replugging the trackpad crashes my system.  Often it
> works fine, but every now and then it triggers `general protection
> faults` (often while opening big applications like Firefox), causes my
> status bar to hang up, and usually ends in a freeze. Sometimes, just
> before the freeze I get thrown back to the console and see a kernel
> panic at the end of the log.
> 
> The laptop is a Thinkpad X200 running stock BIOS, Arch Linux and sway,
> with microcode updates enabled. I could also reproduce the issue with
> Gnome on Wayland. On Xfce I could not reproduce the issue, and also not
> on Fedora (which I installed on the same laptop to the same SSD, for
> testing).
> 
> I'm using the trackpad only via the USB cable, not via bluetooth.
> 
> Attached is a snippet from the dmesg output with debug logging enabled
> (appended `debug` on the kernel cmdline) showing some of the protection
> faults. I uploaded the full dmesg output here [2]. In this specific
> dmesg output, most of the protection faults happened concurrently while
> I was opening Firefox (several times to provoke the crash). A photo of
> the kernel panic can be found here [3].
> 
> This kernel bug report[4] and related arch report[5] seem related to the
> issue, maybe it's even the same issue? However, the kernel bug report
> mentions that the issue only affects linux >=5.8.7. In my case, I could
> reproduce the issue with the following linux versions (installed from
> the Arch Linux archive):
> 
> 	4.20.0
> 	4.20.1
> 	4.20.3
> 	4.20.7
> 	5.0.0
> 	5.0.13
> 	5.4.74
> 	5.2.0
> 	5.8.6
> 	5.8.7
> 	5.8.8
> 	5.9.2, 5.9.4
> 	5.10rc-2
> 
> The USB ID of the trackpad is 05ac:0265.
> 
> Because I'm very inexperienced with kernel debugging I would appreciate
> any help/pointers to what would be wise to test next. If this is likely
> to be an issue with the Linux kernel and not arch-related (unsure, since
> I could not reproduce it on other distros), please tell me so and I will
> post to the kernel bug tracker instead.
> 
> Thanks!
> 
> Merlin Büge
> 
> 
> [0]: https://web.eecs.umich.edu/~cscott/rsi.html
> [1]: https://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid.git/commit/?h=for-next&id=9d7b18668956c411a422d04c712994c5fdb23a4b
> [2]: https://0x0.st/idkH.json
> [3]: https://0x0.st/idkz.jpg
> [4]: https://bugzilla.kernel.org/show_bug.cgi?id=209239
> [5]: https://bugs.archlinux.org/task/67860
> 
> 
> 
> 



-- 
Merlin Büge