Guenter Roeck <linux@xxxxxxxxxxxx> writes: > Hi, > > On Mon, Aug 27, 2018 at 10:47:11AM +0200, Christoph Hellwig wrote: >> There is no reason to leave the per-device dma_ops around when >> deconfiguring a device, so move this code from arm64 into the >> common code. >> Signed-off-by: Christoph Hellwig <hch@xxxxxx> >> Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx> > > This patch causes various ppc images to crash in -next due to NULL > DMA ops in dma_alloc_attrs(). I finally remembered where you autobuilder is :) https://kerneltests.org/builders/qemu-ppc-next/builds/970/steps/qemubuildcommand_1/logs/stdio Looks like mac99 at least is failing. Just reproduced it on my setup. > Looking into the code, the macio driver tries to instantiate on > the 0000:f0:0d.0 PCI address (the driver maps to all Apple PCI IDs) > and fails. This results in a call to arch_teardown_dma_ops(). Later, > the same device pointer is used to instantiate ohci-pci, which > crashes in probe because the dma_ops pointer has been cleared. > > I don't claim to fully understand the code, but to me it looks like > the pci device is allocated and waiting for a driver to attach to. > See arch/powerpc/kernel/pci_of_scan.c:of_create_pci_dev(). > If attaching a driver (here: macio) fails, the same device pointer > is then reused for the next matching driver until a match is found > and the device is successfully instantiated. Of course this fails > quite badly if the device pointer has been scrubbed after the first > failure. > > I don't know if this is generic PCI behavior or ppc specific. > I am copying pci and ppc maintainers for additional input. I would guess this is some PPC special sauce O_o Will have a look. cheers
