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 Content-Length: 1530 Lines: 31 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 -- 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/