Messages in this thread Patch in this message | | | Subject | Re: Regression in 4.11 - PowerPC crashes on boot, bisected to commit 5657933dbb6e | From | Larry Finger <> | Date | Thu, 9 Mar 2017 16:22:01 -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".
Ben,
Attached is a patch that fixes the crash. At the moment, it has my s-o-b, but I do not feel it right to claim authorship. My role should be a Reported-and-tested-by. Please advise.
Larry
From fe51bd0233e10d0eed64cfe177f5d43ca95642a7 Mon Sep 17 00:00:00 2001 From: Larry Finger <Larry.Finger@lwfinger.net> Date: Thu, 9 Mar 2017 16:06:21 -0600 Subject: [PATCH] powerpc: Fix crash introduced with commit 5657933dbb6e
Code inserted during the git merges before kernel 4.11-rc1 caused an early panic quickly followed by a complete shutdown. The traceback was not displayed long enough to read or photograph.
The problem was bisected to commit 5657933dbb6e ("treewide: Move dma_ops from struct dev_archdata into struct device"). The problem was a missing copy of critical information from struct dev_archdata into struct device, leading to the dereference of a null pointer.
Fixes: commit 5657933dbb6e ("treewide: Move dma_ops from struct dev_archdata into struct device") Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net> --- drivers/macintosh/macio_asic.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/drivers/macintosh/macio_asic.c b/drivers/macintosh/macio_asic.c index 3f041b1..f757cef2 100644 --- a/drivers/macintosh/macio_asic.c +++ b/drivers/macintosh/macio_asic.c @@ -392,6 +392,7 @@ static struct macio_dev * macio_add_one_device(struct macio_chip *chip, * To get all the fields, copy all archdata */ dev->ofdev.dev.archdata = chip->lbus.pdev->dev.archdata; + dev->ofdev.dev.dma_ops = chip->lbus.pdev->dev.dma_ops; #endif /* CONFIG_PCI */ #ifdef DEBUG -- 2.10.2
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