Andrew Morton writes:
> On Wed, 24 Dec 2008 13:25:49 +0530 Chandru <chan...@in.ibm.com> wrote:
>
> > On a ppc machine booting linux-2.6.28-rc9 with crashkernel=2...@32m boot
> > parameter causes the kernel to panic while booting. __Following are the
> > console
> > messages...
>
> - Please put [patch] in the Subject: line of patches
>
> - Please choose a suitable title, as per
> Documentation/SubmittingPatches, section 15.
>
> - Please cc suitable mailing lists and maintainers on bug reports and
> on patches.
Dave Hansen was working on this code recently, and this looks a bit
similar to some changes he was making. Dave, what's your opinion on
this patch?
Paul.
> From: Chandru <chan...@in.ibm.com>
>
> When booted with crashkernel=2...@32m or any memory size less than this,
> the system boots properly. The following was the observation.. The
> system comes up with two nodes (0-256M and 256M-4GB). _The crashkernel
> memory reservation spans across these two nodes. _The
> mark_reserved_regions_for_nid() in arch/powerpc/mm/numa.c resizes the
> reserved part of the memory within it as:
>
> _ _ _ _ _ _ if (end_pfn > node_ar.end_pfn)
> _ _ _ _ _ _ _ _ reserve_size = (node_ar.end_pfn << PAGE_SHIFT)
> _ _ _ _ _ _ _ _ _ _ - (start_pfn << PAGE_SHIFT);
>
>
> but the reserve_bootmem_node() in mm/bootmem.c raises the pfn value of end
>
> _ _ end = PFN_UP(physaddr + size);
>
> This causes end to get a value past the last page in the 0-256M node.
> _Again when reserve_bootmem_node() returns,
> _mark_reserved_regions_for_nid() loops around to set the rest of the
> crashkernel memory in the next node as reserved. _ It references
> NODE_DATA(node_ar.nid) and this causes another 'Oops: kernel access of bad
> area' problem. The following changes made the system to boot with any
> amount of crashkernel memory size.
>
> Signed-off-by: Chandru S <chan...@linux.vnet.ibm.com>
> Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
> Cc: Paul Mackerras <pau...@samba.org>
> Signed-off-by: Andrew Morton <a...@linux-foundation.org>
> ---
>
> arch/powerpc/mm/numa.c | 7 ++++---
> mm/bootmem.c | 4 ++++
> 2 files changed, 8 insertions(+), 3 deletions(-)
>
> diff -puN
> arch/powerpc/mm/numa.c~2628-rc9-panics-with-crashkernel=256m-while-booting
> arch/powerpc/mm/numa.c
> ---
> a/arch/powerpc/mm/numa.c~2628-rc9-panics-with-crashkernel=256m-while-booting
> +++ a/arch/powerpc/mm/numa.c
> @@ -995,10 +995,11 @@ void __init do_init_bootmem(void)
> start_pfn, end_pfn);
>
> free_bootmem_with_active_regions(nid, end_pfn);
> + }
> +
> + for_each_online_node(nid) {
> /*
> - * Be very careful about moving this around. Future
> - * calls to careful_allocation() depend on this getting
> - * done correctly.
> + * Be very careful about moving this around.
> */
> mark_reserved_regions_for_nid(nid);
> sparse_memory_present_with_active_regions(nid);
> diff -puN mm/bootmem.c~2628-rc9-panics-with-crashkernel=256m-while-booting
> mm/bootmem.c
> --- a/mm/bootmem.c~2628-rc9-panics-with-crashkernel=256m-while-booting
> +++ a/mm/bootmem.c
> @@ -375,10 +375,14 @@ int __init reserve_bootmem_node(pg_data_
> unsigned long size, int flags)
> {
> unsigned long start, end;
> + bootmem_data_t *bdata = pgdat->bdata;
>
> start = PFN_DOWN(physaddr);
> end = PFN_UP(physaddr + size);
>
> + if (end > bdata->node_low_pfn)
> + end = bdata->node_low_pfn;
> +
> return mark_bootmem_node(pgdat->bdata, start, end, 1, flags);
> }
>
> _
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