This is a note to let you know that I've just added the patch titled

x86/tsc: Provide 'tsc=unstable' boot parameter

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: x86-tsc-provide-tsc-unstable-boot-parameter.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Mon Apr 9 17:09:24 CEST 2018

From: Peter Zijlstra peterz@infradead.org Date: Thu, 13 Apr 2017 14:56:44 +0200 Subject: x86/tsc: Provide 'tsc=unstable' boot parameter

From: Peter Zijlstra peterz@infradead.org

[ Upstream commit 8309f86cd41e8714526867177facf7a316d9be53 ]

Since the clocksource watchdog will only detect broken TSC after the fact, all TSC based clocks will likely have observed non-continuous values before/when switching away from TSC.

Therefore only thing to fully avoid random clock movement when your BIOS randomly mucks with TSC values from SMI handlers is reporting the TSC as unstable at boot.

Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Mike Galbraith efault@gmx.de Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/tsc.c | 2 ++ 1 file changed, 2 insertions(+)

--- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -366,6 +366,8 @@ static int __init tsc_setup(char *str) tsc_clocksource_reliable = 1; if (!strncmp(str, "noirqtime", 9)) no_sched_irq_time = 1; + if (!strcmp(str, "unstable")) + mark_tsc_unstable("boot parameter"); return 1; }

Patches currently in stable-queue which might be from peterz@infradead.org are

queue-4.9/perf-callchain-force-user_ds-when-invoking-perf_callchain_user.patch queue-4.9/perf-report-fix-off-by-one-for-non-activation-frames.patch queue-4.9/x86-efi-disable-runtime-services-on-kexec-kernel-if-booted-with-efi-old_map.patch queue-4.9/perf-tools-fix-copyfile_offset-update-of-output-offset.patch queue-4.9/sched-numa-use-down_read_trylock-for-the-mmap_sem.patch queue-4.9/x86-asm-don-t-use-rbp-as-a-temporary-register-in-csum_partial_copy_generic.patch queue-4.9/perf-core-correct-event-creation-with-perf_format_group.patch queue-4.9/x86-mm-kaslr-use-the-_asm_mul-macro-for-multiplication-to-work-around-clang-incompatibility.patch queue-4.9/x86-tsc-provide-tsc-unstable-boot-parameter.patch queue-4.9/x86-boot-declare-error-as-noreturn.patch queue-4.9/cpuhotplug-link-lock-stacks-for-hotplug-callbacks.patch queue-4.9/perf-core-fix-error-handling-in-perf_event_alloc.patch queue-4.9/sched-deadline-use-the-revised-wakeup-rule-for-suspending-constrained-dl-tasks.patch