Simplify swi for bus_dma.

When a DMA request using bounce pages completes, a swi is triggered to
schedule pending DMA requests using the just-freed bounce pages.  For
a long time this bus_dma swi has been tied to a "virtual memory" swi
(swi_vm).  However, all of the swi_vm implementations are the same and
consist of checking a flag (busdma_swi_pending) which is always true
and if set calling busdma_swi.  I suspect this dates back to the
pre-SMPng days and that the intention was for swi_vm to serve as a
mux.  However, in the current scheme there's no need for the mux.

Instead, remove swi_vm and vm_ih.  Each bus_dma implementation that
uses bounce pages is responsible for creating its own swi (busdma_ih)
which it now schedules directly.  This swi invokes busdma_swi directly
removing the need for busdma_swi_pending.

One consequence is that the swi now works on RISC-V which had previously
failed to invoke busdma_swi from swi_vm.

Reviewed by:	imp, kib
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D33447

1 files changed, 0 insertions, 1 deletions

diff --git a/sys/amd64/include/cpu.h b/sys/amd64/include/cpu.h
index 1b8a552d3e7c..f7732435fc39 100644
--- a/sys/amd64/include/cpu.h
+++ b/sys/amd64/include/cpu.h
@@ -80,7 +80,6 @@ void	cpu_halt(void);
 void	cpu_lock_delay(void);
 void	cpu_reset(void);
 void	fork_trampoline(void);
-void	swi_vm(void *);
 
 /*
  * Return contents of in-cpu fast counter as a sort of "bogo-time"