From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752524Ab3HOVt0 (ORCPT ); Thu, 15 Aug 2013 17:49:26 -0400 Received: from mail-pb0-f49.google.com ([209.85.160.49]:53050 "EHLO mail-pb0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751549Ab3HOVtZ (ORCPT ); Thu, 15 Aug 2013 17:49:25 -0400 MIME-Version: 1.0 In-Reply-To: <20130815205044.GA21599@roeck-us.net> References: <5207B3C3.9080508@roeck-us.net> <20130811220450.GY23006@n2100.arm.linux.org.uk> <52082EF8.10005@roeck-us.net> <20130813034054.GA18218@roeck-us.net> <20130815175428.GA18580@roeck-us.net> <20130815205044.GA21599@roeck-us.net> From: Peter Maydell Date: Thu, 15 Aug 2013 22:49:05 +0100 Message-ID: Subject: Re: [Qemu-devel] SCSI bus failures with qemu-arm in kernel 3.8+ To: Guenter Roeck Cc: Russell King - ARM Linux , Paul Gortmaker , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , QEMU Developers , Arnd Bergmann Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15 August 2013 21:50, Guenter Roeck wrote: > On Thu, Aug 15, 2013 at 07:05:22PM +0100, Peter Maydell wrote: >> It needs to go in the same patch, because a kernel with the fixed >> irq remapping must also tell QEMU it is fixed; if you split the >> two then at the point between the two patches the kernel is >> broken for bisection purposes. >> > Thinking about it - is that really true ? My image with the > patch applied works just fine under qemu 1.5.2, and unless > I am missing something it won't work with qemu 1.4 anyway. > So what exactly is broken ? You're OK unless the kernel happens to pick the same interrupt number to write to PCI_INTERRUPT_LINE as one of the previous broken kernel versions did (in which case QEMU will incorrectly assume you're a broken kernel). This can't happen with the way the kernel is currently picking interrupt numbers (ie with a straightforward relationship between h/w irqs and values written), but as I understand from Arnd there is a plan to move to a different approach ("sparse irqs") at which point this won't hold: http://lists.gnu.org/archive/html/qemu-devel/2013-03/msg04579.html So it's better for the kernel to make sure it gets the behaviour it wants rather than getting unpleasant surprises later. -- PMM From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36768) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VA5QB-00026o-Ex for qemu-devel@nongnu.org; Thu, 15 Aug 2013 17:49:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VA5Q7-0003fi-2S for qemu-devel@nongnu.org; Thu, 15 Aug 2013 17:49:31 -0400 Received: from mail-pb0-f51.google.com ([209.85.160.51]:59551) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VA5Q6-0003fS-T2 for qemu-devel@nongnu.org; Thu, 15 Aug 2013 17:49:27 -0400 Received: by mail-pb0-f51.google.com with SMTP id jt11so1280849pbb.10 for ; Thu, 15 Aug 2013 14:49:25 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20130815205044.GA21599@roeck-us.net> References: <5207B3C3.9080508@roeck-us.net> <20130811220450.GY23006@n2100.arm.linux.org.uk> <52082EF8.10005@roeck-us.net> <20130813034054.GA18218@roeck-us.net> <20130815175428.GA18580@roeck-us.net> <20130815205044.GA21599@roeck-us.net> From: Peter Maydell Date: Thu, 15 Aug 2013 22:49:05 +0100 Message-ID: Content-Type: text/plain; charset=UTF-8 Subject: Re: [Qemu-devel] SCSI bus failures with qemu-arm in kernel 3.8+ List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Guenter Roeck Cc: Russell King - ARM Linux , "linux-kernel@vger.kernel.org" , QEMU Developers , Paul Gortmaker , Arnd Bergmann , "linux-arm-kernel@lists.infradead.org" On 15 August 2013 21:50, Guenter Roeck wrote: > On Thu, Aug 15, 2013 at 07:05:22PM +0100, Peter Maydell wrote: >> It needs to go in the same patch, because a kernel with the fixed >> irq remapping must also tell QEMU it is fixed; if you split the >> two then at the point between the two patches the kernel is >> broken for bisection purposes. >> > Thinking about it - is that really true ? My image with the > patch applied works just fine under qemu 1.5.2, and unless > I am missing something it won't work with qemu 1.4 anyway. > So what exactly is broken ? You're OK unless the kernel happens to pick the same interrupt number to write to PCI_INTERRUPT_LINE as one of the previous broken kernel versions did (in which case QEMU will incorrectly assume you're a broken kernel). This can't happen with the way the kernel is currently picking interrupt numbers (ie with a straightforward relationship between h/w irqs and values written), but as I understand from Arnd there is a plan to move to a different approach ("sparse irqs") at which point this won't hold: http://lists.gnu.org/archive/html/qemu-devel/2013-03/msg04579.html So it's better for the kernel to make sure it gets the behaviour it wants rather than getting unpleasant surprises later. -- PMM From mboxrd@z Thu Jan 1 00:00:00 1970 From: peter.maydell@linaro.org (Peter Maydell) Date: Thu, 15 Aug 2013 22:49:05 +0100 Subject: [Qemu-devel] SCSI bus failures with qemu-arm in kernel 3.8+ In-Reply-To: <20130815205044.GA21599@roeck-us.net> References: <5207B3C3.9080508@roeck-us.net> <20130811220450.GY23006@n2100.arm.linux.org.uk> <52082EF8.10005@roeck-us.net> <20130813034054.GA18218@roeck-us.net> <20130815175428.GA18580@roeck-us.net> <20130815205044.GA21599@roeck-us.net> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 15 August 2013 21:50, Guenter Roeck wrote: > On Thu, Aug 15, 2013 at 07:05:22PM +0100, Peter Maydell wrote: >> It needs to go in the same patch, because a kernel with the fixed >> irq remapping must also tell QEMU it is fixed; if you split the >> two then at the point between the two patches the kernel is >> broken for bisection purposes. >> > Thinking about it - is that really true ? My image with the > patch applied works just fine under qemu 1.5.2, and unless > I am missing something it won't work with qemu 1.4 anyway. > So what exactly is broken ? You're OK unless the kernel happens to pick the same interrupt number to write to PCI_INTERRUPT_LINE as one of the previous broken kernel versions did (in which case QEMU will incorrectly assume you're a broken kernel). This can't happen with the way the kernel is currently picking interrupt numbers (ie with a straightforward relationship between h/w irqs and values written), but as I understand from Arnd there is a plan to move to a different approach ("sparse irqs") at which point this won't hold: http://lists.gnu.org/archive/html/qemu-devel/2013-03/msg04579.html So it's better for the kernel to make sure it gets the behaviour it wants rather than getting unpleasant surprises later. -- PMM