RFC: mpsafe bridge and NIC drivers (vioif and wm)

[Ryota Ozaki <ozaki-r%iij.ad.jp@localhost>]

Hi all,

We're working on making the network stack
(mainly below L3) and device drivers MP-safe.
This RFC is one of the efforts, making bridge
(but STP), vioif and wm MP-safe. Bridging
(L2 forwarding) works in parallel.

The patch set can be found here:
https://github.com/ozaki-r/netbsd-src/tree/experimental/mpsafe-bridge-wm-vioif

Note that applying only this patch has less
fun because all interrupts are delivered to
CPU#0 so that bridge's softint runs on only
the CPU. Please apply another patch set (*);
it allows to change a destination CPU of an
IRQ to a CPU but CPU#0. The following example
changes the destination CPU of IRQ#22 to
CPU#2:
  sysctl -w kern.cpu_affinity.irq="22:2"

With the patch set you can fully try the above
new feature.

(*) https://github.com/knakahara/netbsd-src/commits/k-nakahara-POC-irq-affinity

Any comments are appreciated.

Thanks,
  ozaki-r