On Tue, Nov 19, 2019 at 07:10:23PM -0400, Jason Gunthorpe wrote: > On Tue, Nov 19, 2019 at 04:33:40PM -0500, Michael S. Tsirkin wrote: > > On Tue, Nov 19, 2019 at 03:15:47PM -0400, Jason Gunthorpe wrote: > > > On Tue, Nov 19, 2019 at 01:58:42PM -0500, Michael S. Tsirkin wrote: > > > > On Tue, Nov 19, 2019 at 12:46:32PM -0400, Jason Gunthorpe wrote: > > > > > As always, this is all very hard to tell without actually seeing real > > > > > accelerated drivers implement this. > > > > > > > > > > Your patch series might be a bit premature in this regard. > > > > > > > > Actually drivers implementing this have been posted, haven't they? > > > > See e.g. https://lwn.net/Articles/804379/ > > > > > > Is that a real driver? It looks like another example quality > > > thing. > > > > > > For instance why do we need any of this if it has '#define > > > IFCVF_MDEV_LIMIT 1' ? > > > > > > Surely for this HW just use vfio over the entire PCI function and be > > > done with it? > > > > What this does is allow using it with unmodified virtio drivers > > within guests. You won't get this with passthrough as it only > > implements parts of virtio in hardware. > > I don't mean use vfio to perform passthrough, I mean to use vfio to > implement the software parts in userspace while vfio to talk to the > hardware. You repeated vfio twice here, hard to decode what you meant actually. > kernel -> vfio -> user space virtio driver -> qemu -> guest Exactly what has been implemented for control path. The interface between vfio and userspace is based on virtio which is IMHO much better than a vendor specific one. userspace stays vendor agnostic. > Generally we don't want to see things in the kernel that can be done > in userspace, and to me, at least for this driver, this looks > completely solvable in userspace. I don't think that extends as far as actively encouraging userspace drivers poking at hardware in a vendor specific way. That has lots of security and portability implications and isn't appropriate for everyone. It is kernel's job to abstract hardware away and present a unified interface as far as possible. -- MST
