mapping "random" physical memory into kernel

[Andrew Gallatin]

Scott Long writes:
 > Andrew Gallatin wrote:
 > > Can somebody please remind me what the supported way to establish a
 > > kernel virtual address for a "random" chunk of physical memory is?
 > > I'm currently using pmap_mapdev() directly, but that just feels
 > > dirty...
 > > 
 > > I need to twiddle the settings of an Nvidia NF4 bridge in extended
 > > PCI config space (offset 0x178).  These offsets are not accessible
 > > via normal pci config space writes, but are doable when you use the
 > > 0xe000000 mapping.
 > 
 > Extended pci config space is supported by default on i386, but I
 > haven't gotten around to figuring out the right strategy for
 > amd64.  I'd like to be able to map the entire 256MB range instead
 > of the on-demand approach with i386, but I need to learn more about
 > the various VM maps on amd64 first.

Cool.  It would be great if it worked; I'd love to remove
a bunch of grotty code ;)

 > > 
 > > The problem is that this memory is not really associated with
 > > anything, so a normal bus_alloc_resource() allocation doesn't
 > > seem like it would work.
 > 
 > pmap_mapdev is the correct interface for this.

Except it doesn't appear to exist on sparc64.  But I doubt
we'd ever see an NF4 bridge there, so I suppose I can ifdef
it for i386/amd64.

Drew