swi_vm() and busdma_swi()?

[Venkatesh Srinivas]

Hi,

In the per-mach busdma code, busdma_swi() walks a callback list under
a critical section while add_map_callback() adds to that callback list
under the MPlock and a critical section. Is that perhaps a mistake?

Also -- on amd64 busdma_swi() doesn't look like its called; (on i386
its called via swi_vm(); I don't see how that is called, though it
does register itself as an SWI). Why is this?

-- vs