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authorPeter Zijlstra <peterz@infradead.org>2013-10-24 12:52:06 +0200
committerIngo Molnar <mingo@kernel.org>2013-10-29 12:02:54 +0100
commite00b12e64be9a34ef071de7b6052ca9ea29dd460 (patch)
tree2f3395d06d639550039f3c9aa69c4ad0a4854327 /drivers/hwmon/adm1029.c
parent2c42cfbfe10872929c2ba1f8130e31063ff59b94 (diff)
perf/x86: Further optimize copy_from_user_nmi()
Now that we can deal with nested NMI due to IRET re-enabling NMIs and can deal with faults from NMI by making sure we preserve CR2 over NMIs we can in fact simply access user-space memory from NMI context. So rewrite copy_from_user_nmi() to use __copy_from_user_inatomic() and rework the fault path to do the minimal required work before taking the in_atomic() fault handler. In particular avoid perf_sw_event() which would make perf recurse on itself (it should be harmless as our recursion protections should be able to deal with this -- but why tempt fate). Also rename notify_page_fault() to kprobes_fault() as that is a much better name; there is no notifier in it and its specific to kprobes. Don measured that his worst case NMI path shrunk from ~300K cycles to ~150K cycles. Cc: Stephane Eranian <eranian@google.com> Cc: jmario@redhat.com Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andi Kleen <ak@linux.intel.com> Cc: dave.hansen@linux.intel.com Tested-by: Don Zickus <dzickus@redhat.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20131024105206.GM2490@laptop.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
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