[XEN RFC PATCH 24/40] xen/arm: introduce a helper to parse device tree NUMA distance map

[Wei Chen <wei.chen@xxxxxxx>]

A NUMA aware device tree will provide a "distance-map" node to
describe distance between any two nodes. This patch introduce a
new helper to parse this distance map.

Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
---
 xen/arch/arm/numa_device_tree.c | 67 +++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/xen/arch/arm/numa_device_tree.c b/xen/arch/arm/numa_device_tree.c
index bbe081dcd1..6e0d1d3d9f 100644
--- a/xen/arch/arm/numa_device_tree.c
+++ b/xen/arch/arm/numa_device_tree.c
@@ -200,3 +200,70 @@ device_tree_parse_numa_memory_node(const void *fdt, int 
node,
 
     return 0;
 }
+
+/* Parse NUMA distance map v1 */
+int __init
+device_tree_parse_numa_distance_map_v1(const void *fdt, int node)
+{
+    const struct fdt_property *prop;
+    const __be32 *matrix;
+    int entry_count, len, i;
+
+    printk(XENLOG_INFO "NUMA: parsing numa-distance-map\n");
+
+    prop = fdt_get_property(fdt, node, "distance-matrix", &len);
+    if ( !prop )
+    {
+        printk(XENLOG_WARNING
+               "NUMA: No distance-matrix property in distance-map\n");
+
+        return -EINVAL;
+    }
+
+    if ( len % sizeof(uint32_t) != 0 )
+    {
+        printk(XENLOG_WARNING
+               "distance-matrix in node is not a multiple of u32\n");
+        return -EINVAL;
+    }
+
+    entry_count = len / sizeof(uint32_t);
+    if ( entry_count <= 0 )
+    {
+        printk(XENLOG_WARNING "NUMA: Invalid distance-matrix\n");
+
+        return -EINVAL;
+    }
+
+    matrix = (const __be32 *)prop->data;
+    for ( i = 0; i + 2 < entry_count; i += 3 )
+    {
+        uint32_t from, to, distance;
+
+        from = dt_read_number(matrix, 1);
+        matrix++;
+        to = dt_read_number(matrix, 1);
+        matrix++;
+        distance = dt_read_number(matrix, 1);
+        matrix++;
+
+        if ( (from == to && distance != NUMA_LOCAL_DISTANCE) ||
+            (from != to && distance <= NUMA_LOCAL_DISTANCE) )
+        {
+            printk(XENLOG_WARNING
+                   "Invalid nodes' distance from node#%d to node#%d = %d\n",
+                   from, to, distance);
+            return -EINVAL;
+        }
+
+        printk(XENLOG_INFO "NUMA: distance from node#%d to node#%d = %d\n",
+               from, to, distance);
+        numa_set_distance(from, to, distance);
+
+        /* Set default distance of node B->A same as A->B */
+        if (to > from)
+             numa_set_distance(to, from, distance);
+    }
+
+    return 0;
+}
-- 
2.25.1