We do not use apport and this is easily reproducible. If there is any
pointed information I can provide beyond what I've already submitted,
please let me know.

** Changed in: linux (Ubuntu)
       Status: Incomplete => Confirmed

-- 
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1755627

Title:
  ibrs/ibpb fixes result in excessive kernel logging

Status in linux package in Ubuntu:
  Confirmed

Bug description:
  Since at least kernel 4.4.0-116, every invocation of `sysctl -a`
  results in kernel logs similar to the following:

  % sysctl -a &>/dev/null; dmesg -T | tail -8
  [Wed Mar 14 00:06:36 2018] sysctl_ibrs_enabled = 0, sysctl_ibpb_enabled = 0
  [Wed Mar 14 00:06:36 2018] use_ibrs = 4, use_ibpb = 4
  [Wed Mar 14 00:06:36 2018] read cpu 0 ibrs val 0
  [Wed Mar 14 00:06:36 2018] read cpu 1 ibrs val 0
  [Wed Mar 14 00:06:36 2018] sysctl_ibrs_enabled = 0, sysctl_ibpb_enabled = 0
  [Wed Mar 14 00:06:36 2018] use_ibrs = 4, use_ibpb = 4
  [Wed Mar 14 00:06:36 2018] read cpu 0 ibrs val 0
  [Wed Mar 14 00:06:36 2018] read cpu 1 ibrs val 0

  The output varies with the number of CPUs.

  After digging a bit, it turns out this is triggered upon every read of
  `kernel.ibrs_dump`:

  % for i in {1..3}; do sysctl kernel.ibrs_dump; dmesg -T | tail -8; echo; 
sleep 1; done
  kernel.ibrs_dump = 0
  [Wed Mar 14 00:08:48 2018] sysctl_ibrs_enabled = 0, sysctl_ibpb_enabled = 0
  [Wed Mar 14 00:08:48 2018] use_ibrs = 4, use_ibpb = 4
  [Wed Mar 14 00:08:48 2018] read cpu 0 ibrs val 0
  [Wed Mar 14 00:08:48 2018] read cpu 1 ibrs val 0
  [Wed Mar 14 00:08:48 2018] sysctl_ibrs_enabled = 0, sysctl_ibpb_enabled = 0
  [Wed Mar 14 00:08:48 2018] use_ibrs = 4, use_ibpb = 4
  [Wed Mar 14 00:08:48 2018] read cpu 0 ibrs val 0
  [Wed Mar 14 00:08:48 2018] read cpu 1 ibrs val 0

  kernel.ibrs_dump = 0
  [Wed Mar 14 00:08:49 2018] sysctl_ibrs_enabled = 0, sysctl_ibpb_enabled = 0
  [Wed Mar 14 00:08:49 2018] use_ibrs = 4, use_ibpb = 4
  [Wed Mar 14 00:08:49 2018] read cpu 0 ibrs val 0
  [Wed Mar 14 00:08:49 2018] read cpu 1 ibrs val 0
  [Wed Mar 14 00:08:49 2018] sysctl_ibrs_enabled = 0, sysctl_ibpb_enabled = 0
  [Wed Mar 14 00:08:49 2018] use_ibrs = 4, use_ibpb = 4
  [Wed Mar 14 00:08:49 2018] read cpu 0 ibrs val 0
  [Wed Mar 14 00:08:49 2018] read cpu 1 ibrs val 0

  kernel.ibrs_dump = 0
  [Wed Mar 14 00:08:50 2018] sysctl_ibrs_enabled = 0, sysctl_ibpb_enabled = 0
  [Wed Mar 14 00:08:50 2018] use_ibrs = 4, use_ibpb = 4
  [Wed Mar 14 00:08:50 2018] read cpu 0 ibrs val 0
  [Wed Mar 14 00:08:50 2018] read cpu 1 ibrs val 0
  [Wed Mar 14 00:08:50 2018] sysctl_ibrs_enabled = 0, sysctl_ibpb_enabled = 0
  [Wed Mar 14 00:08:50 2018] use_ibrs = 4, use_ibpb = 4
  [Wed Mar 14 00:08:50 2018] read cpu 0 ibrs val 0
  [Wed Mar 14 00:08:50 2018] read cpu 1 ibrs val 0

  
  Those tests were against an EC2 instance running Ubuntu 4.4.0-116.140-generic 
4.4.98 per /proc/version_signature

  Normally this would not be the biggest concern but we have tooling
  that gathers instance info on a schedule, including sysctl output,
  thus resulting in the kernel ring buffer being full of nothing but
  said output in most cases and hindering live troubleshooting as a
  result.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1755627/+subscriptions

-- 
Mailing list: https://launchpad.net/~kernel-packages
Post to     : kernel-packages@lists.launchpad.net
Unsubscribe : https://launchpad.net/~kernel-packages
More help   : https://help.launchpad.net/ListHelp

Reply via email to