[RFC] PPC64 Exporting memory information through /proc/iomem

[Badari Pulavarty]

On Wed, 2007-10-03 at 08:56 +1000, Paul Mackerras wrote:
> Badari Pulavarty writes:
> 
> > I am trying to get hotplug memory remove working on ppc64.
> > In order to verify a given memory region, if its valid or not -
> > current hotplug-memory patches used /proc/iomem. On IA64 and
> > x86-64 /proc/iomem shows all memory regions. 
> > 
> > I am wondering, if its acceptable to do the same on ppc64 also ?
> 
> I am a bit hesitant to do that, since /proc/iomem is user visible and
> is therefore part of the user/kernel ABI.  Also it feels a bit weird
> to have system RAM in something whose name suggests it's about MMIO.

Yes. That was my first reaction. Until last week, I never realized
that /proc/iomem contains entire memory layout on i386/x86-64 :(

Since i386, x86-64 and ia64 are all doing same thing, I thought breakage
would be minimal (if any) if we do the same on ppc64.

> > Otherwise, we need to add arch-specific hooks in hotplug-remove
> > code to be able to do this.
> 
> Isn't it just a matter of abstracting the test for a valid range of
> memory?  If it's really hard to abstract that, then I guess we can put
> RAM in iomem_resource, but I'd rather not.
> 

Sure. I will work on it and see how ugly it looks.

KAME, are you okay with abstracting the find_next_system_ram() and
let arch provide whatever implementation they want ? (since current
code doesn't work for x86-64 also ?).

Thanks,
Badari