Messages in this thread | | | Subject | Re: Regression in 4.11 - PowerPC crashes on boot, bisected to commit 5657933dbb6e | From | Benjamin Herrenschmidt <> | Date | Tue, 07 Mar 2017 08:48:48 +1100 |
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On Mon, 2017-03-06 at 13:46 -0600, Larry Finger wrote: > 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.
I think the problem is this code in drivers/macintosh/macio_asic.c:
#ifdef CONFIG_PCI /* Set the DMA ops to the ones from the PCI device, this could be * fishy if we didn't know that on PowerMac it's always direct ops * or iommu ops that will work fine * * To get all the fields, copy all archdata */ dev->ofdev.dev.archdata = chip->lbus.pdev->dev.archdata; #endif /* CONFIG_PCI */
This is definitely bad. A quick fix is to copy the new dev->dma_ops field (as well, there is still stuff in archdata that we need too).
A better long term fix is to have a set of macio_dma_ops wrappers that do "the right thing".
Cheers, Ben.
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