[PATCH 1/9] x86/tsc: Provide tsc=unstable boot parameter

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	[PATCH 1/9] x86/tsc: Provide tsc=unstable boot parameter
Date	2017-04-21 19:10 +0200
Message-ID	<tyKef-8vc-57@gated-at.bofh.it> (permalink)
References	<tyKee-8vc-21@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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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>
---
 arch/x86/kernel/tsc.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -374,6 +374,8 @@ 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;
 }

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[PATCH 1/9] x86/tsc: Provide tsc=unstable boot parameter Peter Zijlstra <peterz@infradead.org> - 2017-04-21 19:10 +0200

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