@lscotte - Thanks for reporting the issue. Launchpad will post a note to this bug as soon as the kernel versions containing the fix reach the -proposed archive.
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-- 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: Fix Committed Status in linux source package in Trusty: Fix Committed Status in linux source package in Xenial: Fix Committed Status in linux source package in Artful: Fix Committed 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
