Subject: Re: VAC BUG: PR 6152 (gdb fails on UVM for seperate I&D)
To: Gordon W. Ross <>
From: I. Souvatzis <>
List: tech-kern
Date: 03/23/1999 11:48:14
On Mon, Mar 22, 1999 at 11:52:19PM -0500, Gordon W. Ross wrote:
> I finally had a chance to look at the new pmap_procwr() function,
> and I'm concerned it may not work as presently implemted on any
> Sun machine with a context-dependent VAC.  (Sun3, Sun4, Sun4C)
> The old code worked because the ptrace stuff was careful to
> always switch to the context of the child to change anything.
> With that no longer the case, pmap_procwr() on any Sun VAC
> would need to switch the VAC to the proper context before
> making any changes.  (Note: VAC has multiple H/W contexts.)
> One question:  Why do we not continue to ask the common, MI
> code to switch to the child context while making changes?
> The current way seems to require more MD code...

UVM does these things differently. I don't claim to fully understand (or
remember now) all the details. You would have to check whether 
uvm_io does the right thing on your machines... (it takes a vm_map parameter,
so I would guess it calls some MD hook to do the right thing, but I don't 

Else we'd need a pre-change hook there, and maybe rethink this after 1.4.