On Mon, Feb 27, 2017 at 07:54:35PM +0000, Jean-Philippe Brucker wrote: > It is an important distinction because, if the IOMMU driver reassigns a > PASID while the IOMMU still holds pending PPR targeting that PASID > internally, the PPR will trigger a fault in the wrong address space. The IOMMU driver also controls a devices apbility to issue PPR requests (at least on PCI), so it already knows whether a device has still requests pending or if it even can create new ones. Furhter, the IOMMU driver can already wait for all pending faults to be processed before it shuts down a PASID. So it is not clear to me why the device driver needs to be involved here. When the device driver issues a PASID-unbind call the iommu driver just waits until all pending faults are processed, answers new faults with INVALID, then switch off the devices capability to issue new faults, and then release the PASID. Joerg
