linux-kernel - Re: [PATCH] perf_events: improve DS/BTS/PEBS buffer allocation

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Message-ID: <1284391000.2275.338.camel@laptop>
Date:	Mon, 13 Sep 2010 17:16:40 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	linux-kernel@...r.kernel.org, mingo@...e.hu, paulus@...ba.org,
	davem@...emloft.net, perfmon2-devel@...ts.sf.net,
	eranian@...il.com, robert.richter@....com,
	markus.t.metzger@...el.com
Subject: Re: [PATCH] perf_events: improve DS/BTS/PEBS buffer allocation

On Mon, 2010-09-13 at 17:13 +0200, Stephane Eranian wrote:
> > For now I think you can not do this. vmalloc'ed memory can't be safely
> > accessed from NMIs in x86 because that might fault. And faults from NMIs
> > are not supported. They cause very bad things: return from fault calls
> > iret which reenables NMI, so NMI can nest but in the meantime there is
> > only one NMI stack, so that gets quickly messed up.
> >
> What kind of faults are you talking about here? TLB faults?

Page faults. vmalloc pte setup is lazy.
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