From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751998Ab0IMPRP (ORCPT ); Mon, 13 Sep 2010 11:17:15 -0400 Received: from casper.infradead.org ([85.118.1.10]:36337 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751493Ab0IMPRO convert rfc822-to-8bit (ORCPT ); Mon, 13 Sep 2010 11:17:14 -0400 Subject: Re: [PATCH] perf_events: improve DS/BTS/PEBS buffer allocation From: Peter Zijlstra To: Stephane Eranian Cc: Frederic Weisbecker , Mathieu Desnoyers , linux-kernel@vger.kernel.org, mingo@elte.hu, paulus@samba.org, davem@davemloft.net, perfmon2-devel@lists.sf.net, eranian@gmail.com, robert.richter@amd.com, markus.t.metzger@intel.com In-Reply-To: References: <4c8e3c0c.12d1d80a.73d9.ffffcf21@mx.google.com> <20100913150914.GA6155@nowhere> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Mon, 13 Sep 2010 17:16:40 +0200 Message-ID: <1284391000.2275.338.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.