Re: Access to DMA memory while DMA in progress?

[David Holland <dholland-tech%netbsd.org@localhost>]

On Fri, Oct 27, 2017 at 11:15:34AM -0400, Mouse wrote:
 > Heh.  Well, reading the x86 bus_dma implementation (amd64 doesn't seem
 > to have a separate bus_dma implementation of its own) leads me to think
 > it has no such issues; all POSTREAD does there is copy from the bounce
 > buffer (if the transfer is bounced) and issue an lfence memory barrier.
 > (Hmm, I wonder if the memory barrier needs to be before the memcpy....)

This was discussed at length on irc over the weekend, and the
conclusion seems to be "yes". With a side order of "why can't
architecture manuals ever be clear about these things?"

-- 
David A. Holland
dholland%netbsd.org@localhost