1 files changed, 27 insertions, 0 deletions

diff --git a/arch/x86_64/mm/srat.c b/arch/x86_64/mm/srat.c
index 33340bd1e328..9f69d28652f8 100644
--- a/arch/x86_64/mm/srat.c
+++ b/arch/x86_64/mm/srat.c
@@ -91,9 +91,36 @@ static __init inline int srat_disabled(void)
         return numa_off || acpi_numa < 0;
 }
 
+/*
+ * 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->localities;
+        for (i = 0; i < d; i++) {
+                for (j = 0; j < d; j++)  {
+                        u8 val = slit->entry[d*i + j];
+                        if (i == j) {
+                                if (val != 10)
+                                        return 0;
+                        } else if (val <= 10)
+                                return 0;
+                }
+        }
+        return 1;
+}
+
 /* Callback for SLIT parsing */
 void __init acpi_numa_slit_init(struct acpi_table_slit *slit)
 {
+        if (!slit_valid(slit)) {
+                printk(KERN_INFO "ACPI: SLIT table looks invalid. Not used.\n");
+                return;
+        }
         acpi_slit = slit;
 }