tree 86ede462066ddaab25cc90cde69bd20dce37cac8
parent c6e6c6f20d853493c70a33f3be38e8ef3a373dfa
author Barret Rhoden <brho@cs.berkeley.edu> 1581707971 -0500
committer Barret Rhoden <brho@cs.berkeley.edu> 1583266410 -0500

ioat: support running in a process's address space

Whenever a device is assigned to a process, it's DMA *allocations* come
from the process's dma_arena.  These addresses are user addresses: both
driver and device.  So when we operate in the driver and touch those
bits, we need to be in the user's address space.

Note that dma_map_page() will not return a user-address.  We could try
to wire that up, but it's a bit of a pull.  The issue is that fresh
allocations are easy, but taking an existing kernel page and mapping it
into the user is a little tougher.

Signed-off-by: Barret Rhoden <brho@cs.berkeley.edu>