Re: [PATCH] perf, x86: Optimize intel_pmu_pebs_fixup_ip()

[Linus Torvalds]

On Tue, Oct 22, 2013 at 10:12 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> 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..

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()..

            Linus
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