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From: Byron Stanoszek <gandalf@winds.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 4.18 00/79] 4.18.1-stable review
Date: Wed, 15 Aug 2018 13:24:25 -0400 (EDT)	[thread overview]
Message-ID: <alpine.LNX.2.21.1808151306290.29065@winds.org> (raw)

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


             reply	other threads:[~2018-08-15 17:31 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-15 17:24 Byron Stanoszek [this message]
2018-08-15 17:32 ` [PATCH 4.18 00/79] 4.18.1-stable review Greg Kroah-Hartman
2018-08-16  4:39   ` Byron Stanoszek
2018-08-16 10:12     ` Greg Kroah-Hartman
  -- strict thread matches above, loose matches on Subject: below --
2018-08-14 17:16 Greg Kroah-Hartman
2018-08-15  6:12 ` Greg Kroah-Hartman
2018-08-15 13:16 ` Guenter Roeck
2018-08-15 15:32   ` Greg Kroah-Hartman
2018-08-15 20:12 ` Dan Rue

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