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author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2010-12-08 14:56:23 (GMT) |
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committer | Ingo Molnar <mingo@elte.hu> | 2010-12-16 10:36:42 (GMT) |
commit | 4407204c5c9037763aadce39b025529dfbfcac9e (patch) | |
tree | e9493f1e9f485c5299a07d5b618b6c983029aa65 /kernel | |
parent | 006b20fe4c69189b0d854e5eabf269e50ca86cdd (diff) | |
download | linux-fsl-qoriq-4407204c5c9037763aadce39b025529dfbfcac9e.tar.xz |
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>
Diffstat (limited to 'kernel')
0 files changed, 0 insertions, 0 deletions