Hi Daniel, On Fri, 2020-04-17 at 09:03 +0800, Daniel Drake wrote: > Hi Joerg, > > > Hi, > > > > here is the second version of this patch-set. The first version with > > some more introductory text can be found here: > > > > https://lore.kernel.org/lkml/20200407183742.4344-1-joro@xxxxxxxxxx/ > > Thanks for the continued improvements in this area! > > I may have spotted a problem with setups like VMD. > > The core PCI bus is set up during early boot. > Then, for the PCI bus, we reach iommu_bus_init() -> bus_iommu_probe(). > In there, we call probe_iommu_group() -> dev_iommu_get() for each PCI > device, which allocates dev->iommu in each case. So far so good. > > The problem is that this is the last time that we'll call dev_iommu_get(). > If any PCI bus devices get added after this point, they do not get passed > to dev_iommu_get(). > > So when the vmd module gets loaded later, and creates more PCI devices, > we end up in iommu_bus_notifier() -> iommu_probe_device() > -> __iommu_probe_device() which does: > > dev->iommu->iommu_dev = iommu_dev; > > dev->iommu-> is a NULL dereference because dev_iommu_get() was never > called for this new device. > > Daniel > I should have CCed you on this, but it should temporarily resolve that issue: https://lists.linuxfoundation.org/pipermail/iommu/2020-April/043253.html
