On 2015/6/10 16:30, Luke Gorrie wrote: > On 9 June 2015 at 10:46, Michael S. Tsirkin <mst at redhat.com> wrote: > >> By the way, similarly, host side must re-check avail idx after writing >> used flags. I don't see where snabbswitch does it - is that a bug >> in snabbswitch? > > > Good question. > > Snabb Switch does not use interrupts from the guest. We always set > VRING_F_NO_NOTIFY to tell the guest that it need not interrupt us. Then we > run in poll mode and in practice check the avail ring for new descriptors > every 20us or so.
Yes, host not need guest to notify when in poll mode but host also need to notify guest who use virtio_net when vring is full or emtpy.If host loss this notification guest would stop working. > > So the argument for not needing this check in both Snabb Switch and DPDK is > that we are running poll mode and don't notice whether interrupts are being > sent or not. > > Is that a solid argument or do I misunderstand what the race condition is? > > Cheers, > -Luke >