On 24/05/18 12:50, Ilias Apalodimas wrote: >> Interesting, I hadn't thought about this use-case before. At first I >> thought you were talking about mdev devices assigned to VMs, but I think >> you're referring to mdevs assigned to userspace drivers instead? Out of >> curiosity, is it only theoretical or does someone actually need this? > > There has been some non upstreamed efforts to have mdev and produce userspace > drivers. Huawei is using it on what they call "wrapdrive" for crypto devices and > we did a proof of concept for ethernet interfaces. At the time we choose not to > involve the IOMMU for the reason you mentioned, but having it there would be > good. I'm guessing there were good reasons to do it that way but I wonder, is it not simpler to just have the kernel driver create a /dev/foo, with a standard ioctl/mmap/poll interface? Here VFIO adds a layer of indirection, and since the mediating driver has to implement these operations already, what is gained? Thanks, Jean
