On Wed, Oct 23, 2013 at 08:09:53AM +0100, Linus Torvalds wrote: > On Tue, Oct 22, 2013 at 10:12 PM, Peter Zijlstra <pet...@infradead.org> wrote: > >> > >> Careful! There is one magic piece of state that you need to > >> save-and-restore if you do this, namely %cr2. Taking a page fault > >> always writes to %cr2, and we must *not* corrupt it in the NMI > >> handler. > > > > It looks like this is already dealt with (a similar thing is done for > > i386). > > Oh, ok then, we should be good to go. I wonder why we needed that > special "_nmi()" version, then..
Ah, the whole fault from nmi trickery from Steve is from after we did the copy_from_user_nmi() thing. We're only just catching up :-) > Please do check that NMI increment the irq-counts etc.. Otherwise > you'll need to add the explicit "pagefault_disable/enable()" pair > around the __copy_from_user_inatomic().. Yeah, we add NMI_OFFSET to preempt_count on nmi_enter. I'll also make sure to test we actually hit the fault path by concurrently running something like: while :; echo 1 > /proc/sys/vm/drop_caches ; done while doing perf top or so.. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
