Re: [libvirt] [PATCH 10/18] qemu: Support filesystem model=virtio-{non-}transitional

On Thu, Jan 17, 2019 at 12:52:37PM -0500, Cole Robinson wrote: > Add <filesystem> model handling for virtio transitional devices. Ex: > > <filesystem type='mount' model='virtio-transitional'> > ... > </filesystem > > * "virtio-transitional" maps to qemu "virtio-9p-pci-transitional" > * "virtio-non-transitional" maps to qemu "virtio-9p-pci-non-transitional" For QEMU the <filesystem> element currently implies the 9p filesystem passthrough impl. We already have a need to reuse it for USB-MTP filesystem sharing, and quite soon we'll have to support virtio-fs too. The virtio-fs module is essentially fuse-over-virtio IIUC. In fact I wonder why we're not just calling that device virtio-fuse to make it explicit ! Anyway the point is that model=virtio-transitional is potentially ambiguous, depending on how we intend to deal with this. I was at first thinking of model="virtio-9p|virtio-fs|usb-mtp" to deal with the existing issue, but you're proposing using model already. I'm a little mixed about how to best dovetail with the transitional stuff. We could use 'model' stuff but expand it: virtio-9p virtio-9p-transitional virtio-9p-non-transitional virtio-fs usb-mtp IIUC, we don't need a -transitional/-non-transitional variant for virtio-fs since it will be a modern device only - same as with virtio-gpu. Or we could do things different and invert something like a 'protocol' concept for the filesystem. <filesystem type='mount'> <target dir="foo" protocol="9p|mtp|fuse"/> </filesystem>