From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765707AbZFOScD (ORCPT ); Mon, 15 Jun 2009 14:32:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1765732AbZFOSbv (ORCPT ); Mon, 15 Jun 2009 14:31:51 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:51529 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759239AbZFOSbv (ORCPT ); Mon, 15 Jun 2009 14:31:51 -0400 Date: Mon, 15 Jun 2009 11:30:05 -0700 (PDT) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: Mathieu Desnoyers cc: Ingo Molnar , mingo@redhat.com, hpa@zytor.com, paulus@samba.org, acme@redhat.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, penberg@cs.helsinki.fi, vegard.nossum@gmail.com, efault@gmx.de, jeremy@goop.org, npiggin@suse.de, tglx@linutronix.de, linux-tip-commits@vger.kernel.org Subject: Re: [tip:perfcounters/core] perf_counter: x86: Fix call-chain support to use NMI-safe methods In-Reply-To: <20090615180527.GB4201@Krystal> Message-ID: References: <20090615171845.GA7664@elte.hu> <20090615180527.GB4201@Krystal> User-Agent: Alpine 2.01 (LFD 1184 2008-12-16) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 15 Jun 2009, Mathieu Desnoyers wrote: > > Hrm, would it be possible to save the c2 register upon nmi handler entry > and restore it before iret instead ? Yes, that would work as well, and be less subtle. It still does have the same worries about CPU's not being all that happy about writing to %cr2 (we do it when restoring CPU state at resume time, but nobody has ever _cared_ before, so I don't know if it matters). Linus