Re: [PATCH 0/2] Fix TSC issues on (some) AMD Ryzen based systems

[Paul Menzel <pmenzel@molgen.mpg.de>]

Dear Jan,


Am 29.01.19 um 20:33 schrieb Paul Menzel:

> Thank you for adding me to the CC list.
> 
> 
> Am 29.01.19 um 11:23 schrieb Jan H. Schönherr:
>> My newly acquired AMD Ryzen Threadripper based system seems to have
>> some TSC quirks, which go away once the system is up.
>>
>> Given the discussion in https://lkml.org/lkml/2019/1/28/1356
>> I don't seem to be the only one, and it does not seem to be
>> Threadripper specific.
>>
>> The first patch addresses presumably SMI interruptions, that occur
>> on my system at a 60 Hz frequency. They take too long, making the
>> existing code fail. The patch makes that code more resilient.
>> (These interruptions go away at some point during boot; also proven
>> by the fact, that I don't have any TSC issues, when kexecing into
>> a new kernel.)
>>
>> The second patch prevents TSC going unstable when resuming from S3.
>> This may have a similar source, but is certainly more weird: the
>> TSC is observed to go backwards on CPU0 by about 200 to 500 cycles
>> compared to other CPUs every once in a while, as long as its sibling
>> (CPU16 in my case) hasn't been resumed yet. (I did some experiments
>> with CPU hotplug before and after suspend, but apart from reproducing
>> the issue and verifying the "fix", I got nowhere.)
>>
>> The patches are against v4.20.
>>
>> Jan H. Schönherr (2):
>>    x86/tsc: Allow quick PIT calibration despite interruptions
>>    cpu/hotplug: Unfreeze sibling CPU first on resume from S3
>>
>>   arch/x86/kernel/tsc.c | 80 +++++++++++++++++++++++++------------------
>>   kernel/cpu.c          | 34 ++++++++++++------
>>   2 files changed, 70 insertions(+), 44 deletions(-)
> 
> I successfully tested both applied on Linus’ current master branch
> (v5.0-rc4-1-g4aa9fc2a435a).
> 
>> [    0.000000] DMI: HP HP EliteDesk 705 G4 MT/83E7, BIOS Q06 Ver. 02.04.01 09/14/2018
>> [    0.000000] tsc: Fast TSC calibration using PIT
>> [    0.000000] tsc: Detected 3616.864 MHz processor

Please do not forget to tag both patches for the stable releases
by adding the tag.

 > CC: stable@vger.kernel.org


Kind regards,

Paul