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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2010-12-08 15:56:23 +0100
committerIngo Molnar <mingo@elte.hu>2010-12-16 11:36:42 +0100
commit4407204c5c9037763aadce39b025529dfbfcac9e (patch)
treee9493f1e9f485c5299a07d5b618b6c983029aa65 /init
parent006b20fe4c69189b0d854e5eabf269e50ca86cdd (diff)
downloadlinux-2.6.38-lt-ux500-4407204c5c9037763aadce39b025529dfbfcac9e.tar.gz
perf, x86: Detect broken BIOSes that corrupt the PMU
Some BIOSes use PMU resources, which can cause various bugs: - Non-working or erratic PMU based statistics - the PMU can end up counting the wrong thing, resulting in misleading statistics - Profiling can stop working or it can profile the wrong thing - A non-working or erratic NMI watchdog that cannot be relied on - The kernel may disturb whatever thing the BIOS tries to use the PMU for - possibly causing hardware malfunction in extreme cases. - ... and other forms of potential misbehavior Various forms of such misbehavior has been observed in practice - there are BIOSes that just corrupt the PMU state, consequences be damned. The PMU is a CPU resource that is handled by the kernel and the BIOS stealing+corrupting it is not acceptable nor robust, so we detect it, warn about it and further refuse to touch the PMU ourselves. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Jason Wessel <jason.wessel@windriver.com> Cc: Don Zickus <dzickus@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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