Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750991AbWJ0O4x (ORCPT ); Fri, 27 Oct 2006 10:56:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752201AbWJ0O4x (ORCPT ); Fri, 27 Oct 2006 10:56:53 -0400 Received: from colin.muc.de ([193.149.48.1]:2322 "EHLO mail.muc.de") by vger.kernel.org with ESMTP id S1750991AbWJ0O4w (ORCPT ); Fri, 27 Oct 2006 10:56:52 -0400 Date: 27 Oct 2006 16:56:50 +0200 Date: Fri, 27 Oct 2006 16:56:50 +0200 From: Andi Kleen To: Zachary Amsden Cc: Andrew Morton , Rusty Russell , Jeremy Fitzhardinge , Chris Wright , Virtualization Mailing List , Linux Kernel Mailing List Subject: Re: [PATCH 1/5] Skip timer works.patch Message-ID: <20061027145650.GA37582@muc.de> References: <200610200009.k9K09MrS027558@zach-dev.vmware.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200610200009.k9K09MrS027558@zach-dev.vmware.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1502 Lines: 35 On Thu, Oct 19, 2006 at 05:09:22PM -0700, Zachary Amsden wrote: > Add a way to disable the timer IRQ routing check via a boot option. The > VMI timer code uses this to avoid triggering the pester Mingo code, which > probes for some very unusual and broken motherboard routings. It fires > 100% of the time when using a paravirtual delay mechanism instead of > using a realtime delay, since there is no elapsed real time, and the 4 timer > IRQs have not yet been delivered. You mean paravirtualized udelay will not actually wait? This implies that you can't ever use any real timer in that kind of guest, right? > > In addition, it is entirely possible, though improbable, that this bug > could surface on real hardware which picks a particularly bad time to enter > SMM mode, causing a long latency during one of the timer IRQs. We already have a no timer check option. But: > > While here, make check_timer be __init. So how is this supposed to work? The hypervisor would always pass that option? If yes that would seem rather hackish to me. We should probably instead probe in some way if we have the required timer hardware. The paravirt kernel should know anyways it is paravirt and that it doesn't need to probe for flakey hardware. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/