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 18:43:18 -0600 |
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On 03/06/2017 03:48 PM, Benjamin Herrenschmidt wrote: > 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".
The one-line fix that copies dma_ops does indeed fix the problem.
What do you want to do from here? I could prepare a q & d patch to resolve the regression, or would you prefer to do "the right thing" now?
Larry
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