> -----Original Message----- > From: Paul Menzel <pmen...@molgen.mpg.de> > Sent: Thursday, June 11, 2020 3:59 AM > To: Thomas Gleixner; Ingo Molnar; Borislav Petkov > Cc: x...@kernel.org; LKML; Limonciello, Mario; Hans de Goede; Christian > Kellner; linux...@vger.kernel.org > Subject: Intel laptop: Starting with `maxcpus=1` and then bringing other > CPUs online freezes system > > > [EXTERNAL EMAIL] > > Dear Linux folks, > > > This is an interesting one. On a Dell Precision 3540 with a dedicated > AMD graphics card, and with Debian Sid/unstable and Linux 5.6.14, there > are several strange issues (one example [1]). > > Starting the system, and adding `maxcpus=1` to the Linux command line, > the system starts. > > Trying to bring up more CPUs, works for the first one, but fails for the > second. The system freezes then. Nothing is dumped on the Linux virtual > terminal. > > In my limited tests, this always happens, when the system runs on > batteries, that means, without the power cord plugged in. But I was also > able to reproduce it with the USB Type-C power cable plugged in. But > sometimes it works (to bring all other seven CPUs online). > > Please find the Linux messages up to bringing CPU 1 online attached with > no power cord plugged in, and the messages of a successful operation. > > Is this expected? I’d appreciated tips, if it’s possible to debug this > further. > > > Kind regards, > > Paul > > > [1]: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1883065
From some other similar reports I've heard this could be related to the ucode loading causing a freeze. I would suggest trying to disable the Intel ucode loader with the initramfs as a debugging tactic.
