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
