1 files changed, 27 insertions, 4 deletions

diff --git a/drivers/acpi/numa.c b/drivers/acpi/numa.c
index 5d59cb33b1a5..658e5f3abae0 100644
--- a/drivers/acpi/numa.c
+++ b/drivers/acpi/numa.c
@@ -140,19 +140,42 @@ acpi_table_print_srat_entry(struct acpi_subtable_header *header)
         }
 }
 
+/*
+ * A lot of BIOS fill in 10 (= no distance) everywhere. This messes
+ * up the NUMA heuristics which wants the local node to have a smaller
+ * distance than the others.
+ * Do some quick checks here and only use the SLIT if it passes.
+ */
+static __init int slit_valid(struct acpi_table_slit *slit)
+{
+        int i, j;
+        int d = slit->locality_count;
+        for (i = 0; i < d; i++) {
+                for (j = 0; j < d; j++)  {
+                        u8 val = slit->entry[d*i + j];
+                        if (i == j) {
+                                if (val != LOCAL_DISTANCE)
+                                        return 0;
+                        } else if (val <= LOCAL_DISTANCE)
+                                return 0;
+                }
+        }
+        return 1;
+}
+
 static int __init acpi_parse_slit(struct acpi_table_header *table)
 {
         struct acpi_table_slit *slit;
-        u32 localities;
 
         if (!table)
                 return -EINVAL;
 
         slit = (struct acpi_table_slit *)table;
 
-        /* downcast just for %llu vs %lu for i386/ia64  */
-        localities = (u32) slit->locality_count;
-
+        if (!slit_valid(slit)) {
+                printk(KERN_INFO "ACPI: SLIT table looks invalid. Not used.\n");
+                return -EINVAL;
+        }
         acpi_numa_slit_init(slit);
 
         return 0;