From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753986AbdCFTsO (ORCPT ); Mon, 6 Mar 2017 14:48:14 -0500 Received: from mail-ot0-f194.google.com ([74.125.82.194]:33536 "EHLO mail-ot0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932951AbdCFTsD (ORCPT ); Mon, 6 Mar 2017 14:48:03 -0500 Subject: Re: Regression in 4.11 - PowerPC crashes on boot, bisected to commit 5657933dbb6e To: Bart Van Assche , "regressions@leemhuis.info" , "benh@kernel.crashing.org" References: <5bc9c08f-58aa-ef26-8891-4837e2d4184b@lwfinger.net> <1488431644.2870.64.camel@kernel.crashing.org> <1488823339.3125.3.camel@sandisk.com> Cc: "linux-kernel@vger.kernel.org" From: Larry Finger Message-ID: <1f134650-adcf-ef11-21aa-fad9d1dc3c29@lwfinger.net> Date: Mon, 6 Mar 2017 13:46:38 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <1488823339.3125.3.camel@sandisk.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/06/2017 12:02 PM, Bart Van Assche wrote: > On Thu, 2017-03-02 at 16:14 +1100, Benjamin Herrenschmidt wrote: >> On Wed, 2017-03-01 at 21:26 -0600, Larry Finger wrote: >>> My Powerbook G4 Aluminum generates a fatal splat early in the boot process, just >>> after identifying the driver for the disk. Unfortunately, it turns off almost >>> immediately, thus I cannot report the message. After this bug has been >>> triggered, the system clock has been reset to Dec. 31, 1969. I assume this is a >>> side effect of an uncontrolled DMA operation. >>> >>> This problem has been bisected to commit 5657933dbb6e ("treewide: Move dma_ops >>> from struct dev_archdata into struct device"). >> >> Side effect of a crash during boot... the PMU gets upset when we crash while >> there's a request in flight, that's probably what is happening. >> >> As to why that commit is broken, I don't have time to look into it right now, >> maybe next week of nobody beats me to it. > > The results of my attempts so far to create a PPC VM: > * I have not found a CPU / architecture / CD bus type / combination for which the > Gentoo installation CD was able to recognize the boot medium > (http://distfiles.gentoo.org/releases/ppc/autobuilds/20140713/install-powerpc-minimal-20140713.iso). > * Same problem with the openSUSE Leap CD: apparently that software does not recognize > the qemu SCSI CD > (http://mirror.datto.com/opensuse/ports/ppc/distribution/leap/42.2/iso/openSUSE-Leap-42.2-NET-ppc64le-Build0156-Media.iso). > * openSUSE Tumbleweed recognizes the qemu SCSI CD. After it has loaded the installation > software however it displays an message reporting that an error occurred during > installation and displays a menu. Making a selection from that menu is not possible > because the only key from the keyboard it recognizes is "Enter" > (http://mirror.datto.com/opensuse/ports/ppc/tumbleweed/iso/openSUSE-Tumbleweed-DVD-ppc64-Snapshot20170303-Media.iso). > > Does anyone have a suggestion for how to proceed? I was able to create a PPC emulation with debian-8.7.1-powerpc-CD-1.iso following the instructions in https://gmplib.org/~tege/qemu.html. My only problem was that "-net tap" fails and I did not find any way to get networking working. After looking at the screen through a number of crashes, I have determined that the top entry in the traceback comes from dmam_alloc_coherent(). I have not been able to see the offset to determine which BUG_ON call in that routine is being triggered. I tried to modify panic() to see if I could keep the screen on longer after the failure, but no joy so far. Larry