[RFC 17/18] arm: mm: Add SW emulation for ARM domain manager feature

[Nicolas Pitre]

On Mon, 22 Mar 2010, Daniel Walker wrote:

> On Mon, 2010-03-22 at 14:58 -0400, Nicolas Pitre wrote:
> > On Mon, 22 Mar 2010, Daniel Walker wrote:
> > 
> > > On Mon, 2010-01-25 at 16:40 +0000, Catalin Marinas wrote:
> > > > Hi Daniel,
> > > > 
> > > > On Mon, 2010-01-11 at 22:47 +0000, Daniel Walker wrote:
> > > > > Do not set domain manager bits in cp15 dacr.  Emulate using SW.  Add
> > > > > kernel hooks to handle domain changes, permission faults, and context
> > > > > switches.
> > > > 
> > > > In case you were not aware, there's a patch around (I think since 2007)
> > > > that removes the domain switching entirely from the kernel (given that
> > > > they have been deprecated for some time and may disappear completely in
> > > > the future):
> > > > 
> > > > http://lists.infradead.org/pipermail/linux-arm-kernel/2009-December/005616.html
> > > > 
> > > 
> > > I didn't find this in 2.6.34 ? Are you re-writing it? Why has it been
> > > around so long out of mainline?
> > 
> > Because no real hardware out there needed it until recently, i.e. 
> > inertia.
> 
> Current MSM hardware needs it, just to cover up a defect in the
> processor. At least that's what this thread was originally about.

Some other processors should need it too for some architecturally 
defined reasons. Would be a good thing if you could remove your 
emulation and replace it with this patch, and confirm it works for you 
by providing Tested-by tags.


Nicolas