On Tue, May 19, 2015 at 12:08:39PM +0800, Zhiqiang Zhang wrote: > commit e00b12e64be9a34ef071de7b6052ca9ea29dd460 upstream > > 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@xxxxxxxxxx> > Cc: jmario@xxxxxxxxxx > Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxx> > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx> > Cc: dave.hansen@xxxxxxxxxxxxxxx > Tested-by: Don Zickus <dzickus@xxxxxxxxxx> > Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Link: http://lkml.kernel.org/r/20131024105206.GM2490@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> > [zhangzhiqiang: backport to 3.10: Did you make sure all the nested NMI fixes are in 3.10? -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html