On Mon, Jul 07, 2014 at 07:58:18AM -0300, Ezequiel Garcia wrote: > On 05 Jul 01:59 PM, Greg Kroah-Hartman wrote: > > On Sat, Jul 05, 2014 at 12:03:08PM -0300, Ezequiel Garcia wrote: > > > After following Gregory's stacktrace (also reproduced here): > > > > > > [<c02451f8>] (iommu_bus_notifier) from [<c00512e8>] > > > (notifier_call_chain+0x64/0x9c) > > > [<c00512e8>] (notifier_call_chain) from [<c00514cc>] > > > (__blocking_notifier_call_chain+0x40/0x58) > > > [<c00514cc>] (__blocking_notifier_call_chain) from [<c00514f8>] > > > (blocking_notifier_call_chain+0x14/0x1c) > > > [<c00514f8>] (blocking_notifier_call_chain) from [<c01d225c>] > > > (device_add+0x424/0x524) > > > [<c01d225c>] (device_add) from [<c0186d90>] (pci_device_add+0xec/0x110) > > > [<c0186d90>] (pci_device_add) from [<c0186e54>] > > > (pci_scan_single_device+0xa0/0xac) > > > > > > I added a few printks and found that the problem is that the > > > iommu_bus_notifier is > > > called for the 'pci' bus type, which has a null iommu_ops. > > > > > > On 04 Jul 10:47 AM, Laurent Pinchart wrote: > > > [..] > > > > > > > > We need a quick fix for v3.16, ... > > > > > > Therefore, a quick fix would be to simply check for that: > > > > > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > > > index e5555fc..b712cb2 100644 > > > --- a/drivers/iommu/iommu.c > > > +++ b/drivers/iommu/iommu.c > > > @@ -536,6 +536,9 @@ static int iommu_bus_notifier(struct notifier_block > > > *nb, > > > struct iommu_group *group; > > > unsigned long group_action = 0; > > > > > > + if (!ops) > > > + return 0; > > > + > > > /* > > > * ADD/DEL call into iommu driver ops if provided, which may > > > * result in ADD/DEL notifiers to group->notifier > > > > > > This (nasty workaround?) patch makes the problem go away. > > > > > > [..] > > > > > So it also boot well in 3.15 and then failed in 3.16-rc3. I hope it > > > > > will > > > > > help the developers of the OMAP IOMMU driver to fix it. > > > > > > > > Thank you. I've had a look at the OMAP IOMMU driver changes between > > > > v3.15 and > > > > v3.16-rc3, and didn't find at first sight any change that could explain > > > > the > > > > crash. > > > > > > > > 286f600 iommu/omap: Fix map protection value handling > > > > 67b779d iommu/omap: Remove comment about supporting single page > > > > mappings only > > > > f7129a0 iommu/omap: Fix 'no page for' debug message in > > > > flush_iotlb_page() > > > > 5acc97d iommu/omap: Move to_iommu definition from omap-iopgtable.h > > > > 2ac6133 iommu/omap: Remove omap_iommu_domain_has_cap() function > > > > d760e3e iommu/omap: Correct init value of iotlb_entry valid field > > > > > > > > Could you try reverting those changes and retest ? If the problem > > > > doesn't > > > > disappear, we'll need to look somewhere else. > > > > > > > > > > I reverted the above commits but nothing changed. I'm far from being an > > > expert, > > > but it sounds odd to have this bus notifier (that got registered for the > > > platform bus type) called by a pci bus type. > > > > Why wouldn't the PCI bus set this up for its devices? Are you > > "assuming" you know the bus type and that's the issue? > > > > Thanks for looking at this. > > I guess I snipped the thread and lost most of the information about the panic. > Here's the original bug report: > > http://www.spinics.net/lists/arm-kernel/msg344059.html > > The problem reported involves enabling OMAP IOMMU driver and not any other > IOMMU > driver. Doing some tracing and adding a few prints, we found that > omap_iommu_init() sets a bus notifier for the platform bus type: > > omap_iommu_init -> bus_set_iommu -> iommu_bus_init: > > static void iommu_bus_init(struct bus_type *bus, struct iommu_ops *ops) > { > bus_register_notifier(bus, &iommu_bus_nb); > bus_for_each_dev(bus, NULL, ops, add_iommu_group); > } > > But the iommu bus notifier gets called for the 'pci' bus type, which > has the iommu_ops field NULL (since it hasn't been set for iommu).
So this is what needs to be figured out, how is the notifier being called with a PCI device? Who else called iommu_bus_init() for the PCI bus? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
