> From: Alex Williamson <alex.williamson@xxxxxxxxxx> > Sent: Tuesday, June 13, 2023 11:04 PM > > > > > > > > > > > > > > > Unless I missed it, we've not described that vfio device cdev access is > > > > > still bound by IOMMU group semantics, ie. there can be one DMA owner > > > > > for the group. That's a pretty common failure point for multi-function > > > > > consumer device use cases, so the why, where, and how it fails should > > > > > be well covered. > > > > > > > > Yes. this needs to be documented. How about below words: > > > > > > > > vfio device cdev access is still bound by IOMMU group semantics, ie. there > > > > can be only one DMA owner for the group. Devices belonging to the same > > > > group can not be bound to multiple iommufd_ctx. > > > > > > ... or shared between native kernel and vfio drivers. > > > > I suppose you mean the devices in one group are bound to different > > drivers. right? > > Essentially, but we need to be careful that we're developing multiple > vfio drivers for a given bus now, which is why I try to distinguish > between the two sets of drivers. Thanks, Indeed. There are a set of vfio drivers. Even pci-stub can be considered in this set? Perhaps, it is more precise to say : or shared between drivers that set the struct pci_driver::driver_managed_dma flag and the drivers that do not. Regards, Yi Liu
