On Mon, Nov 18, 2013 at 02:52:53PM +1000, Dave Airlie wrote: > So after talking to a few people at kvm forum I think the GPU code > should probably use the dataplane stuff from the outset, > > The main advantages I think this gives me is being able to dequeue > objects from the vq from a thread and send irq vectors from there as > well. > > Though since it appears the dataplane stuff is kvm specific (at least > the irq handling), I was wondering how I should deal with fallbacks > for non-kvm operation, and quite how much falling back I need to do. > > Can I still use the dataplane/vring code from the normal bottom half > handlers or do I have to write separate code for both situations.
As of today, there are still two vring implementations in hw/virtio/virtio.c and hw/virtio/dataplane/vring.c. This means it isn't clean and easy to integrate into a new device yet. Existing dataplane devices basically take advantage of the fact that the non-dataplane version sets up the device before I/O. Paolo can give you details on the latest thread-safe memory API stuff and whether it's already usable for virtio. Regarding irqfd, we could emulate it in TCG using an EventNotifier (eventfd). At that point I think it's no longer kvm-specific. Stefan
