Messages in this thread | | | Subject | Re: Regression in 4.11 - PowerPC crashes on boot, bisected to commit 5657933dbb6e | From | Larry Finger <> | Date | Mon, 6 Mar 2017 13:46:38 -0600 |
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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
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