With DISCONTIGMEM, the mapping between a pfn and its owning node is initialized using data provided by the BIOS or from the command line. However, the initialization may fail if the extents are not aligned to section boundary (64M).
The symptom of this bug is an early boot failure in pfn_to_page(), as it tries to access NODE_DATA(__nid) using index from an unitialized element of the physnode_map[] array. While the bug is always present, it is more likely to be hit in kdump kernels on large machines, because: 1. The memory map for a kdump kernel is specified as exactmap, and exactmap is more likely to be unaligned. 2. Large reservations are more likely to span across a 64M boundary. Signed-off-by: Petr Tesarik <[email protected]> --- arch/x86/mm/numa_32.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/arch/x86/mm/numa_32.c b/arch/x86/mm/numa_32.c index 0342d27..f278b04 100644 --- a/arch/x86/mm/numa_32.c +++ b/arch/x86/mm/numa_32.c @@ -46,15 +46,16 @@ EXPORT_SYMBOL(physnode_map); void memory_present(int nid, unsigned long start, unsigned long end) { - unsigned long pfn; + unsigned long sect, endsect; printk(KERN_INFO "Node: %d, start_pfn: %lx, end_pfn: %lx\n", nid, start, end); printk(KERN_DEBUG " Setting physnode_map array to node %d for pfns:\n", nid); printk(KERN_DEBUG " "); - for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) { - physnode_map[pfn / PAGES_PER_SECTION] = nid; - printk(KERN_CONT "%lx ", pfn); + endsect = (end - 1) / PAGES_PER_SECTION; + for (sect = start / PAGES_PER_SECTION; sect <= endsect; ++sect) { + physnode_map[sect] = nid; + printk(KERN_CONT "%lx ", sect * PAGES_PER_SECTION); } printk(KERN_CONT "\n"); } -- 1.8.4.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
