x86_64: disable srat when numa emulation succeeds

When NUMA emulation succeeds, acpi_numa needs to be set to -1 so that
srat_disabled() will always return true.  We won't be calling
acpi_scan_nodes() or registering the true nodes we've found.

[hugh@veritas.com: Fix x86_64 CONFIG_NUMA_EMU build: acpi_numa needs CONFIG_ACPI_NUMA]
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/x86_64/mm/numa.c

@@ -473,9 +473,13 @@ static int __init numa_emulation(unsigned long start_pfn, unsigned long end_pfn)
 
 	/*
 	 * We need to vacate all active ranges that may have been registered by
-	 * SRAT.
+	 * SRAT and set acpi_numa to -1 so that srat_disabled() always returns
+	 * true.  NUMA emulation has succeeded so we will not scan ACPI nodes.
 	 */
 	remove_all_active_ranges();
+#ifdef CONFIG_ACPI_NUMA
+	acpi_numa = -1;
+#endif
 	for_each_node_mask(i, node_possible_map) {
 		e820_register_active_regions(i, nodes[i].start >> PAGE_SHIFT,
 						nodes[i].end >> PAGE_SHIFT);