[PATCH v6 03/17] xen/arm: implement node distance helpers for Arm

[Henry Wang <Henry.Wang@xxxxxxx>]

From: Wei Chen <wei.chen@xxxxxxx>

We will parse NUMA nodes distances from device tree. So we need
a matrix to record the distances between any two nodes we parsed.
Accordingly, we provide this node_set_distance API for device tree
NUMA to set the distance for any two nodes in this patch. When
NUMA initialization failed, __node_distance will return
NUMA_REMOTE_DISTANCE, this will help us avoid doing rollback
for distance maxtrix when NUMA initialization failed.

As both x86 and Arm have implemented __node_distance, so we move
its declaration from asm/numa.h to xen/numa.h. At same time, the
outdated u8 return value of x86 has been changed to unsigned char.

Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
Signed-off-by: Henry Wang <Henry.Wang@xxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx> # non-Arm parts
---
v6:
- Rebase on top of staging without code changes.
v4 -> v5:
- Coding style (extra blank line and printk variable type) and
  in-code comment fixes and improvements.
- Move the from/to range check in numa_set_distance() to caller,
- Drop the unnecessary check ensured by caller in numa_set_distance().
- Rework the invalid distance check in numa_set_distance() following
  Linux, add more in-code comments about these distance checks.
v3 -> v4:
- s/definition/declaration/ in commit message.
- Add Acked-by tag from Jan for non-Arm parts.
- Drop unnecessary initializer for node_distance_map. Pre-set the
  distance map to NUMA_NO_DISTANCE.
- Drop NUMA_DISTANCE_UDF_MIN and its usage.
- Drop EXPORT_SYMBOL(__node_distance).
- Rework __node_distance()'s return value logic.
v2 -> v3:
- Use __ro_after_init for node_distance_map.
- Correct format of if condition identation in numa_set_distance().
- Drop the unnecessary change to the year of copyright.
- Use ARRAY_SIZE() to determine node_distance_map's row, column size.
v1 -> v2:
- Use unsigned int/char instead of uint32_t/u8.
- Re-org the commit message.
---
 xen/arch/arm/Makefile           |  1 +
 xen/arch/arm/include/asm/numa.h | 12 ++++++++
 xen/arch/arm/numa.c             | 51 +++++++++++++++++++++++++++++++++
 xen/arch/x86/include/asm/numa.h |  1 -
 xen/arch/x86/srat.c             |  2 +-
 xen/include/xen/numa.h          |  1 +
 6 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
index 7bf07e9920..86e0e47e22 100644
--- a/xen/arch/arm/Makefile
+++ b/xen/arch/arm/Makefile
@@ -38,6 +38,7 @@ obj-$(CONFIG_LIVEPATCH) += livepatch.o
 obj-y += mem_access.o
 obj-y += mm.o
 obj-y += monitor.o
+obj-$(CONFIG_NUMA) += numa.o
 obj-y += p2m.o
 obj-y += percpu.o
 obj-y += platform.o
diff --git a/xen/arch/arm/include/asm/numa.h b/xen/arch/arm/include/asm/numa.h
index 83f60ad05b..96c856a9f7 100644
--- a/xen/arch/arm/include/asm/numa.h
+++ b/xen/arch/arm/include/asm/numa.h
@@ -22,7 +22,19 @@ typedef u8 nodeid_t;
  */
 #define NR_NODE_MEMBLKS NR_MEM_BANKS
 
+/*
+ * In ACPI spec, 0-9 are the reserved values for node distance,
+ * 10 indicates local node distance, 20 indicates remote node
+ * distance. Set node distance map in device tree will follow
+ * the ACPI's definition.
+ */
+#define NUMA_DISTANCE_UDF_MAX   9
+#define NUMA_LOCAL_DISTANCE     10
+#define NUMA_REMOTE_DISTANCE    20
+
 extern bool numa_disabled(void);
+extern void numa_set_distance(nodeid_t from, nodeid_t to,
+                              unsigned int distance);
 
 #else
 
diff --git a/xen/arch/arm/numa.c b/xen/arch/arm/numa.c
index eb5d0632cb..31332a6ea7 100644
--- a/xen/arch/arm/numa.c
+++ b/xen/arch/arm/numa.c
@@ -28,6 +28,11 @@ enum dt_numa_status {
 
 static enum dt_numa_status __ro_after_init device_tree_numa = DT_NUMA_DEFAULT;
 
+static unsigned char __ro_after_init
+node_distance_map[MAX_NUMNODES][MAX_NUMNODES] = {
+    [0 ... MAX_NUMNODES - 1] = { [0 ... MAX_NUMNODES - 1] = NUMA_NO_DISTANCE }
+};
+
 void __init numa_fw_bad(void)
 {
     printk(KERN_ERR "NUMA: device tree numa info table not used.\n");
@@ -48,3 +53,49 @@ int __init arch_numa_setup(const char *opt)
 {
     return -EINVAL;
 }
+
+void __init numa_set_distance(nodeid_t from, nodeid_t to,
+                              unsigned int distance)
+{
+    /*
+     * Since the NUMA device tree binding does not clearly specify the valid
+     * range of node distance, here we keep consistent with the ACPI, whose
+     * SLIT table uses 1 byte to describe the node distance. Hence node
+     * distances that cannot fit in 1 byte are invalid. Also, node distance
+     * 0-9 are undefined values.
+     * Reject all above-mentioned invalid distance values.
+     */
+    if ( (uint8_t)distance != distance || distance <= NUMA_DISTANCE_UDF_MAX )
+    {
+        printk(XENLOG_WARNING
+               "NUMA: invalid distance: from=%"PRIu8" to=%"PRIu8" 
distance=%u\n",
+               from, to, distance);
+        return;
+    }
+
+    node_distance_map[from][to] = distance;
+}
+
+unsigned char __node_distance(nodeid_t from, nodeid_t to)
+{
+    if ( from == to )
+        return NUMA_LOCAL_DISTANCE;
+
+    /*
+     * When NUMA is off, any distance will be treated as unreachable, so
+     * directly return NUMA_NO_DISTANCE from here as an optimization.
+     */
+    if ( numa_disabled() )
+        return NUMA_NO_DISTANCE;
+
+    /*
+     * Check whether the nodes are in the matrix range.
+     * When any node is out of range, except from and to nodes are the
+     * same (see above), we treat them as unreachable.
+     */
+    if ( from >= ARRAY_SIZE(node_distance_map) ||
+         to >= ARRAY_SIZE(node_distance_map[0]) )
+        return NUMA_NO_DISTANCE;
+
+    return node_distance_map[from][to];
+}
diff --git a/xen/arch/x86/include/asm/numa.h b/xen/arch/x86/include/asm/numa.h
index 7866afa408..45456ac441 100644
--- a/xen/arch/x86/include/asm/numa.h
+++ b/xen/arch/x86/include/asm/numa.h
@@ -22,7 +22,6 @@ extern void init_cpu_to_node(void);
 #define arch_want_default_dmazone() (num_online_nodes() > 1)
 
 void srat_parse_regions(paddr_t addr);
-extern u8 __node_distance(nodeid_t a, nodeid_t b);
 unsigned int arch_get_dma_bitsize(void);
 
 #endif
diff --git a/xen/arch/x86/srat.c b/xen/arch/x86/srat.c
index 3f70338e6e..e55a749ad5 100644
--- a/xen/arch/x86/srat.c
+++ b/xen/arch/x86/srat.c
@@ -324,7 +324,7 @@ unsigned int numa_node_to_arch_nid(nodeid_t n)
        return 0;
 }
 
-u8 __node_distance(nodeid_t a, nodeid_t b)
+unsigned char __node_distance(nodeid_t a, nodeid_t b)
 {
        unsigned index;
        u8 slit_val;
diff --git a/xen/include/xen/numa.h b/xen/include/xen/numa.h
index 3e215db1ca..bb9a3d2591 100644
--- a/xen/include/xen/numa.h
+++ b/xen/include/xen/numa.h
@@ -114,6 +114,7 @@ extern bool numa_memblks_available(void);
 extern bool numa_update_node_memblks(nodeid_t node, unsigned int arch_nid,
                                      paddr_t start, paddr_t size, bool 
hotplug);
 extern void numa_set_processor_nodes_parsed(nodeid_t node);
+extern unsigned char __node_distance(nodeid_t a, nodeid_t b);
 
 #else
 
-- 
2.25.1