> A VFIO DMABUF can export a subset of a BAR to userspace by fd; add > support for mmap() of this fd. This provides another route for a > process to map BARs, in which the process can only map a specific > subset of a BAR represented by the exported DMABUF. > > mmap() support enables userspace drivers to safely delegate BAR > sub-ranges to other processes by sharing a DMABUF fd, without having > to share the (omnipotent) VFIO device fd with them. > > Since the main VFIO BAR mmap() is now DMABUF-aware, the new mmap() reuses > the existing vm_ops. > > The lifecycle of an exported DMABUF remains decoupled from that of the > device fd it came from, i.e. the device fd could be closed with DMABUF > VMAs present, meaning a fault on a VMA could happen concurrently with > vfio_pci_dma_buf_cleanup(). > > To deal with this scenario, the fault handler now temporarily takes a > VFIO device registration to ensure the vdev remains valid, and then > vdev locks can be taken. > > Signed-off-by: Matt Evans <[email protected]>
Sashiko has reviewed this patch and found no issues. It looks great! -- Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=8
