3 files changed, 70 insertions, 0 deletions

diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index f5510d889a22..fbeaaf416610 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -496,6 +496,7 @@ static bool __init numa_meminfo_cover_memory(const struct numa_meminfo *mi)
 
 static int __init numa_register_memblks(struct numa_meminfo *mi)
 {
+        unsigned long uninitialized_var(pfn_align);
         int i, nid;
 
         /* Account for nodes with cpus and no memory */
@@ -511,6 +512,20 @@ static int __init numa_register_memblks(struct numa_meminfo *mi)
 
         /* for out of order entries */
         sort_node_map();
+
+        /*
+         * If sections array is gonna be used for pfn -> nid mapping, check
+         * whether its granularity is fine enough.
+         */
+#ifdef NODE_NOT_IN_PAGE_FLAGS
+        pfn_align = node_map_pfn_alignment();
+        if (pfn_align && pfn_align < PAGES_PER_SECTION) {
+                printk(KERN_WARNING "Node alignment %LuMB < min %LuMB, rejecting NUMA config\n",
+                       PFN_PHYS(pfn_align) >> 20,
+                       PFN_PHYS(PAGES_PER_SECTION) >> 20);
+                return -EINVAL;
+        }
+#endif
         if (!numa_meminfo_cover_memory(mi))
                 return -EINVAL;
 
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 9670f71d7be9..c70a326b8f26 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1313,6 +1313,7 @@ extern void remove_active_range(unsigned int nid, unsigned long start_pfn,
                                         unsigned long end_pfn);
 extern void remove_all_active_ranges(void);
 void sort_node_map(void);
+unsigned long node_map_pfn_alignment(void);
 unsigned long __absent_pages_in_range(int nid, unsigned long start_pfn,
                                                 unsigned long end_pfn);
 extern unsigned long absent_pages_in_range(unsigned long start_pfn,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4e8985acdab8..9119faae6e6a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4585,6 +4585,60 @@ void __init sort_node_map(void)
                         cmp_node_active_region, NULL);
 }
 
+/**
+ * node_map_pfn_alignment - determine the maximum internode alignment
+ *
+ * This function should be called after node map is populated and sorted.
+ * It calculates the maximum power of two alignment which can distinguish
+ * all the nodes.
+ *
+ * For example, if all nodes are 1GiB and aligned to 1GiB, the return value
+ * would indicate 1GiB alignment with (1 << (30 - PAGE_SHIFT)).  If the
+ * nodes are shifted by 256MiB, 256MiB.  Note that if only the last node is
+ * shifted, 1GiB is enough and this function will indicate so.
+ *
+ * This is used to test whether pfn -> nid mapping of the chosen memory
+ * model has fine enough granularity to avoid incorrect mapping for the
+ * populated node map.
+ *
+ * Returns the determined alignment in pfn's.  0 if there is no alignment
+ * requirement (single node).
+ */
+unsigned long __init node_map_pfn_alignment(void)
+{
+        unsigned long accl_mask = 0, last_end = 0;
+        int last_nid = -1;
+        int i;
+
+        for_each_active_range_index_in_nid(i, MAX_NUMNODES) {
+                int nid = early_node_map[i].nid;
+                unsigned long start = early_node_map[i].start_pfn;
+                unsigned long end = early_node_map[i].end_pfn;
+                unsigned long mask;
+
+                if (!start || last_nid < 0 || last_nid == nid) {
+                        last_nid = nid;
+                        last_end = end;
+                        continue;
+                }
+
+                /*
+                 * Start with a mask granular enough to pin-point to the
+                 * start pfn and tick off bits one-by-one until it becomes
+                 * too coarse to separate the current node from the last.
+                 */
+                mask = ~((1 << __ffs(start)) - 1);
+                while (mask && last_end <= (start & (mask << 1)))
+                        mask <<= 1;
+
+                /* accumulate all internode masks */
+                accl_mask |= mask;
+        }
+
+        /* convert mask to number of pages */
+        return ~accl_mask + 1;
+}
+
 /* Find the lowest pfn for a node */
 static unsigned long __init find_min_pfn_for_node(int nid)
 {