had a kvm switch once and it sucked even for just ps2.  now i find it
rare for the need to access the real keyboard/mouse of a machine.
expecialy in the case of plan9 where you can use drawterm or vnc.

in case you want to use 2 monitors and only switch for keyboard/mouse
input you can use the synergy client [1] for plan9.  (expecting you are
using window/unix on the other machine)

[1] /n/sources/contrib/cinap_lenrek/synergy.tgz

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cinap