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Bug 1547854

Summary: Latest rt56 real time kernel on Intel i9 has broken TSC
Product: Red Hat Enterprise MRG Reporter: Kazu Yoshida <kyoshida>
Component: realtime-kernelAssignee: Daniel Bristot de Oliveira <daolivei>
Status: CLOSED ERRATA QA Contact: Jiri Kastner <jkastner>
Severity: high Docs Contact: Petr Bokoc <pbokoc>
Priority: high    
Version: 2.5CC: bhu, daolivei, lgoncalv, mgaykar, pbokoc, prarit, williams
Target Milestone: 2.5   
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: kernel-rt-3.10.0-693.24.1.rt56.609.el6rt Doc Type: Bug Fix
Doc Text:
Intel Core X-Series (Skylake) processors use a hardcoded Time Stamp Counter (TSC) frequency of 25 MHz. In some cases this can be imprecise and lead to timing-related problems such as time drift, timers being triggered early, or TSC clock instability. This update mitigates these problems by no longer using the "native_calibrate_tsc()" function to define the TSC frequency. Refined calibration is now used to update the clock rate accordingly in these cases.
 Story Points: ---
Clone Of: Environment:
Last Closed: 2018-04-17 15:34:33 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description Kazu Yoshida 2018-02-22 06:27:27 UTC 
Description of problem:

Latest rt56 real time kernel on Intel i9 has broken TSC

Feb 20 06:55:24 uk01ds300 kernel: tsc: Detected 2600.000 MHz processor
Feb 20 06:55:24 uk01ds300 kernel: TSC synchronization [CPU#0 -> CPU#1]:
Feb 20 06:55:24 uk01ds300 kernel: Measured 115899160216746 cycles TSC warp between CPUs, turning off TSC clock.
Feb 20 06:55:24 uk01ds300 kernel: tsc: Marking TSC unstable due to check_tsc_sync_source failed


Version-Release number of selected component (if applicable):

Red Hat Enterprise MRG Realtime 2.5
3.10.0-693.17.1.rt56.604.el6rt.x86_64 

CPU: 
model name      : Intel(R) Core(TM) i9-7980XE CPU @ 2.60GHz

X299 chipset 


How reproducible:

100% at every boot


Steps to Reproduce:
1. Boot into 3.10.0-693.17.1.rt56.604.el6rt.x86_64


Actual results:

TSC clock turns off.


Expected results:

TSC clock to work correctly.


Additional info:

The issue seems to be fixed in upstream.

https://patchwork.kernel.org/patch/10177655/

https://patchwork.kernel.org/patch/10128789/
https://patchwork.kernel.org/patch/10128793/
https://patchwork.kernel.org/patch/10128791/
Comment 23 Daniel Bristot de Oliveira 2018-04-13 13:17:56 UTC 
Hi Petr,

It is ok, Thanks!

-- Daniel
Comment 25 errata-xmlrpc 2018-04-17 15:34:33 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2018:1170