x86_64: fake pxm-to-node mapping for fake numa

For NUMA emulation, our SLIT should represent the true NUMA topology of the
system but our proximity domain to node ID mapping needs to reflect the
emulated state.

When NUMA emulation has successfully setup fake nodes on the system, a new
function, acpi_fake_nodes() is called.  This function determines the proximity
domain (_PXM) for each true node found on the system.  It then finds which
emulated nodes have been allocated on this true node as determined by its
starting address.  The node ID to PXM mapping is changed so that each fake
node ID points to the PXM of the true node that it is located on.

If the machine failed to register a SLIT, then we assume there is no special
requirement for emulated node affinity so we use the default LOCAL_DISTANCE,
which is newly exported to this code, as our measurement if the emulated nodes
appear in the same PXM.  Otherwise, we use REMOTE_DISTANCE.

PXM_INVAL and NID_INVAL are also exported to the ACPI header file so that we
can compare node_to_pxm() results in generic code (in this case, the SRAT
code).

Cc: Len Brown <lenb@kernel.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 74 insertions, 3 deletions

diff --git a/arch/x86_64/mm/numa.c b/arch/x86_64/mm/numa.c
index 51548947ad3b..30bf8043984d 100644
--- a/arch/x86_64/mm/numa.c
+++ b/arch/x86_64/mm/numa.c
@@ -484,6 +484,7 @@ out:
                                                 nodes[i].end >> PAGE_SHIFT);
                 setup_node_bootmem(i, nodes[i].start, nodes[i].end);
         }
+        acpi_fake_nodes(nodes, num_nodes);
         numa_init_array();
         return 0;
 }
diff --git a/arch/x86_64/mm/srat.c b/arch/x86_64/mm/srat.c
index 0e0725db20b7..7ac8ff333e84 100644
--- a/arch/x86_64/mm/srat.c
+++ b/arch/x86_64/mm/srat.c
@@ -350,7 +350,7 @@ acpi_numa_memory_affinity_init(struct acpi_srat_mem_affinity *ma)
 
 /* Sanity check to catch more bad SRATs (they are amazingly common).
    Make sure the PXMs cover all memory. */
-static int nodes_cover_memory(void)
+static int __init nodes_cover_memory(const struct bootnode *nodes)
 {
         int i;
         unsigned long pxmram, e820ram;
@@ -406,7 +406,7 @@ int __init acpi_scan_nodes(unsigned long start, unsigned long end)
                 }
         }
 
-        if (!nodes_cover_memory()) {
+        if (!nodes_cover_memory(nodes)) {
                 bad_srat();
                 return -1;
         }
@@ -440,6 +440,75 @@ int __init acpi_scan_nodes(unsigned long start, unsigned long end)
         return 0;
 }
 
+#ifdef CONFIG_NUMA_EMU
+static int __init find_node_by_addr(unsigned long addr)
+{
+        int ret = NUMA_NO_NODE;
+        int i;
+
+        for_each_node_mask(i, nodes_parsed) {
+                /*
+                 * Find the real node that this emulated node appears on.  For
+                 * the sake of simplicity, we only use a real node's starting
+                 * address to determine which emulated node it appears on.
+                 */
+                if (addr >= nodes[i].start && addr < nodes[i].end) {
+                        ret = i;
+                        break;
+                }
+        }
+        return i;
+}
+
+/*
+ * In NUMA emulation, we need to setup proximity domain (_PXM) to node ID
+ * mappings that respect the real ACPI topology but reflect our emulated
+ * environment.  For each emulated node, we find which real node it appears on
+ * and create PXM to NID mappings for those fake nodes which mirror that
+ * locality.  SLIT will now represent the correct distances between emulated
+ * nodes as a result of the real topology.
+ */
+void __init acpi_fake_nodes(const struct bootnode *fake_nodes, int num_nodes)
+{
+        int i;
+        int fake_node_to_pxm_map[MAX_NUMNODES] = {
+                [0 ... MAX_NUMNODES-1] = PXM_INVAL
+        };
+
+        printk(KERN_INFO "Faking PXM affinity for fake nodes on real "
+                         "topology.\n");
+        for (i = 0; i < num_nodes; i++) {
+                int nid, pxm;
+
+                nid = find_node_by_addr(fake_nodes[i].start);
+                if (nid == NUMA_NO_NODE)
+                        continue;
+                pxm = node_to_pxm(nid);
+                if (pxm == PXM_INVAL)
+                        continue;
+                fake_node_to_pxm_map[i] = pxm;
+        }
+        for (i = 0; i < num_nodes; i++)
+                __acpi_map_pxm_to_node(fake_node_to_pxm_map[i], i);
+
+        nodes_clear(nodes_parsed);
+        for (i = 0; i < num_nodes; i++)
+                if (fake_nodes[i].start != fake_nodes[i].end)
+                        node_set(i, nodes_parsed);
+        WARN_ON(!nodes_cover_memory(fake_nodes));
+}
+
+static int null_slit_node_compare(int a, int b)
+{
+        return node_to_pxm(a) == node_to_pxm(b);
+}
+#else
+static int null_slit_node_compare(int a, int b)
+{
+        return a == b;
+}
+#endif /* CONFIG_NUMA_EMU */
+
 void __init srat_reserve_add_area(int nodeid)
 {
         if (found_add_area && nodes_add[nodeid].end) {
@@ -464,7 +533,8 @@ int __node_distance(int a, int b)
         int index;
 
         if (!acpi_slit)
-                return a == b ? LOCAL_DISTANCE : REMOTE_DISTANCE;
+                return null_slit_node_compare(a, b) ? LOCAL_DISTANCE :
+                                                      REMOTE_DISTANCE;
         index = acpi_slit->locality_count * node_to_pxm(a);
         return acpi_slit->entry[index + node_to_pxm(b)];
 }