Rusty Russell wrote: > On Tuesday 04 March 2008 16:08:00 Max Krasnyansky wrote: >>> The problem with this approach is that for what I'm doing, the packets >>> aren't nicely arranged somewhere; they're in random process memory. >> That's fine. RX/TX descriptors would not contain the data itself. They'd >> contain pointers to actual packets (ie just like the NIC takes physical >> memory address and DMAs data in/out). >> The allows for sending/receiving packets without syscalls and fits nicely >> with the async schemes like GSO. > > Yes, yes it does. That would be a very nice extension (it's orthogonal to > this patch though, so should we get Dave to take these for 2.6.25?). It's orthogonal in general I agree. The only concern is whether we should keep extending existing driver API (ie adding more flags like TUN_NO_PI, etc) or go straight to the new/better ring based API. I do not have a strong preference one way or the other. So I guess I'm saying I'd be ok with Dave taking them for 2.6.25, but that API may be obsolete when the ring based thing comes out. > And as it happens, virtio already has such a structure: virtio_ring. See > linux/virtio_ring.h. I'll take a look. >>> The structure is for virtio, I'm just borrowing it for tap because it's >>> already there. We could rename it and move it out to its own header, but >>> if so we should do that before 2.6.25 is released. >> If we do the whole enchilada with the RX/TX rings then we probably do not >> even need it. I'm thinking that RX/TX descriptor would include everything >> you need for the GSO and stuff. >> I meant do not need it for the TUN/TAP driver that is. Is it used anywhere >> else ? > > Just for the linux virtio drivers. Reusing it for tun/tap was an > afterthought. It just meant I could pass the same structure straight thru, > though, which is nice. > > The userspace->kernel problem is very similar to the guest->host problem, so > it doesn't surprise me if we end up with very similar (identical?) > interfaces. > > Take a look at virtio_ring.h, virtio_ring.c and Documentation/lguest/lguest.c > to see how we use it... Thanx for the pointers. Max _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
