On Fri, Oct 23, 2009 at 02:01:23PM +1030, Rusty Russell wrote: > On Thu, 22 Oct 2009 08:07:45 pm Michael S. Tsirkin wrote: > > Imagine an indirect entry where NEXT bit is also set. > > Hmm, so it's not obvious whether the kvm userspace code handles it > correctly either.
You mean qemu? I think it doesn't, either: code there looks basically like lguest. > Want to hack something up to use NEXT + INDIRECT, then we can actually test > it? If it doesn't work, this will have to be a new feature bit. > > Also, we have a limitation that you can't have more descriptors than the ring > size, even with indirect, due to overzealous checks... Yes ... so I wonder: do we want to fix all this and add a feature bit, or wait until some guest actually wants to use such descriptors? For vhost, I implemented INDIRECT without this limitation since it looked neater to me to have a separate function for indirect anyway. This is because direct virtqueues are virtually contigious, so I can access them just by copy from user, but indirect can be spread around and so I have to go through extra translations. > Thanks, > Rusty. _______________________________________________ Virtualization mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/virtualization
