Re: [PATCH] drivers/base: export gpl (un)register_memory_notifier

From: Badari Pulavarty
Date: Thu Feb 14 2008 - 12:34:03 EST


On Thu, 2008-02-14 at 09:12 -0800, Dave Hansen wrote:
..
> > > > - Use currently other not exported functions in kernel/resource.c, like
> > > > walk_memory_resource (where we would still need the maximum
> > > possible number
> > > > of pages NR_MEM_SECTIONS)
> > >
> > > It isn't the act of exporting that's the problem. It's making sure that
> > > the exports won't be prone to abuse and that people are using them
> > > properly. You should assume that you can export and use
> > > walk_memory_resource().
> >
> > So this seems to come down to a basic question:
> > New hardware seems to have a tendency to get "private MMUs",
> > which need private mappings from the kernel address space into a
> > "HW defined address space with potentially unique characteristics"
> > RDMA in Openfabrics with global MR is the most prominent example heading
> > there
>
> That's not a question. ;)
>
> Please explain to me why walk_memory_resource() is insufficient for your
> needs. I've now pointed it out to you at least 3 times.

I am not sure what you are trying to do with walk_memory_resource(). The
behavior is different on ppc64. Hotplug memory usage assumes that all
the memory resources (all system memory, not just IOMEM) are represented
in /proc/iomem. Its the case with i386 and ia64. But on ppc64 is
contains ONLY iomem related. Paulus didn't want to export all the system
memory into /proc/iomem on ppc64. So I had to workaround by providing
arch-specific walk_memory_resource() function for ppc64.

Thanks,
Badari

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/