From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265621AbUBPOUZ (ORCPT ); Mon, 16 Feb 2004 09:20:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265602AbUBPOUZ (ORCPT ); Mon, 16 Feb 2004 09:20:25 -0500 Received: from aun.it.uu.se ([130.238.12.36]:2228 "EHLO aun.it.uu.se") by vger.kernel.org with ESMTP id S265915AbUBPOUS (ORCPT ); Mon, 16 Feb 2004 09:20:18 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <16432.53658.676333.134293@alkaid.it.uu.se> Date: Mon, 16 Feb 2004 15:20:10 +0100 From: Mikael Pettersson To: Will Cohen Cc: Philippe Elie , Andrew Morton , linux-kernel@vger.kernel.org, John Levon Subject: Re: [PATCH] oprofile add Pentium Mobile support In-Reply-To: <4030CBC3.6060605@redhat.com> References: <20040212224152.GE316@zaniah> <16432.39480.817800.21083@alkaid.it.uu.se> <4030CBC3.6060605@redhat.com> X-Mailer: VM 7.17 under Emacs 20.7.1 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Will Cohen writes: > Mikael Pettersson wrote: > > Philippe Elie writes: > > > From: Will Cohen > > > > > > Add oprofile support for Pentium Mobile (P6 core). Pentium Mobile needs > > > to unmask LVPTC vector, since it doesn't hurt other P6 core based cpus > > > we do it unconditionally for all these. > > > > [Patch talking about the Pentium-M.] > > > > I can find no support in Intel's documentation (IA32 Volume 3, > > 25366813.pdf) that Pentium-M:s need to unmask LVTPC. > > > > How certain are you of this? Is this an undocumented hardware > > quirk? If it is documented, please indicate where. > > I have tested it on a Pentium M machine. Without the unmask LVTPC the > nmi handler collected precisely one interrupt. With the LVTPC unmask the > OProfile data collection worked normally. > > > It's my theory that P4 added the auto-masking to help PEBS > > buffer overflow situations, but since P-M doesn't have PEBS, > > they shouldn't have had to change this on P-M as well. > > OTOH, it's certainly possible they changed it by accident. > > My theory is that the Pentium M uses same bus interface and local apic > as the Pentium M. Thus, the Pentium M shares the Pentium 4 need to > unmask LVTPC. Sounds reasonable and is consistent with other P-M vs P6 changes. > > One way of testing this would be to run a P-M with > > nmi_watchdog=2. If the NMI counter keeps ticking, then > > LVTPC does not need unmasking. > > Yes, I tested the nmi watchdog and it currently does not work on the > Pentium M. It doesn't get the later interrupts and states it is stuck. That confirms the "undocumented HW quirk" theory. Thanks. I'll fix the (in-kernel) NMI watchdog and (out-of-kernel) perfctr drivers. /Mikael