linux-kernel - Re: [PATCH 4.18 00/79] 4.18.1-stable review

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Date:   Wed, 15 Aug 2018 13:24:25 -0400 (EDT)
From:   Byron Stanoszek <gandalf@...ds.org>
To:     linux-kernel@...r.kernel.org
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 4.18 00/79] 4.18.1-stable review

Hi Greg & Thomas,

I'd like to report a regression in Linux 4.18.1 regarding the L1TF patches.

The kernel no longer thinks I have SMT enabled in the BIOS. This works fine in
4.18.0.

Not sure if this matters, but in my particular 4-core system, my third core is
broken (core #2). So I must boot using "maxcpus=2" and then online the other
cores & SMT threads at startup using:

echo 1 > /sys/devices/system/cpu/cpu3/online
echo 1 > /sys/devices/system/cpu/cpu4/online
echo 1 > /sys/devices/system/cpu/cpu5/online
echo 1 > /sys/devices/system/cpu/cpu7/online

In 4.18.0, dmesg shows:

smpboot: Booting Node 0 Processor 3 APIC 0x6
smpboot: Booting Node 0 Processor 4 APIC 0x1
smpboot: Booting Node 0 Processor 5 APIC 0x3
smpboot: Booting Node 0 Processor 7 APIC 0x7

In 4.18.1, dmesg shows:

smpboot: Booting Node 0 Processor 3 APIC 0x6
smpboot: Booting Node 0 Processor 4 APIC 0x1
smpboot: CPU 4 is now offline
smpboot: Booting Node 0 Processor 5 APIC 0x3
smpboot: CPU 5 is now offline
smpboot: Booting Node 0 Processor 7 APIC 0x7
smpboot: CPU 7 is now offline

and I get an "Operation cancelled" error in the shell when trying to online 4,
5, and 7.

In 4.18.1, /sys/devices/system/cpu/smt/control says "notsupported".

  - - -

A possible second regression is the following:

My CPU normally runs at 3600 MHz. I usually run my CPU at 2800 MHz to keep from
overheating under full load (it is a fanless system). I do this by running
"echo 1 > /sys/class/thermal/cooling_device5/cur_state", and confirm with "cat
/proc/cpuinfo" (shows 2800).

This works in 4.18.0 but not in 4.18.1. I get no error from the "echo" command
(and the state reads back as "1"), but the CPU remains running at 3600 MHz.

Thanks,
  -Byron