[PATCH 1/2] powerpc: add 16K/64K pages support for the 44x PPC32 architectures.

[Hollis Blanchard]

On Wed, Oct 22, 2008 at 9:28 AM, Christian Ehrhardt
<ehrhardt at linux.vnet.ibm.com> wrote:
> Hi Ilya,
> I just tried your patch on my 440 board because it would help us in our
> environment.
> Unfortunately I run into a bug on early boot (mark_bootmem).
>
> A log can be found in this mail, this is the bug when running with 64k page
> size.
> I tried this with and without your 2/2 265k patch and also with page size
> configured to 16k, the error is the same in all cases.
>
> I used an earlier version of your patch in the past and it worked fine.
> Applying this old patch causes the same problem.
> Therefore I expect that there was some other code changed that breaks with
> page size != 4k.

This patch seems to solve the problem for me, but I have to run and
haven't yet worked out if it's the right fix.

diff --git a/mm/bootmem.c b/mm/bootmem.c
--- a/mm/bootmem.c
+++ b/mm/bootmem.c
@@ -300,7 +300,7 @@ static int __init mark_bootmem(unsigned
                unsigned long max;

                if (pos < bdata->node_min_pfn ||
-                   pos >= bdata->node_low_pfn) {
+                   pos > bdata->node_low_pfn) {
                        BUG_ON(pos != start);
                        continue;
                }
@@ -399,7 +399,7 @@ int __init reserve_bootmem(unsigned long
        unsigned long start, end;

        start = PFN_DOWN(addr);
-       end = PFN_UP(addr + size);
+       end = PFN_DOWN(addr + size);

        return mark_bootmem(start, end, 1, flags);
 }

Looks like the breakage may have been accidentally introduced by
Johannes Weiner <hannes at saeurebad.de> on Jul 24 (post 2.6.26).

FWIW, the boards Christian and I are hitting the problem on are
Sequoias with 256MB of RAM. cuImage is reporting only 0xffff000 bytes
of RAM though, which may be exacerbating the situation.

-Hollis