ACPI: eliminate restriction on ACPI processor ID range

Rather than storing the reference acpi_device pointers in an ACPI-ID-
indexed array (and having a bogus BUG_ON() check on a platform provided
value), use a radix tree instead.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/drivers/acpi/processor_core.c
+++ b/drivers/acpi/processor_core.c
@@ -513,7 +513,14 @@ static int acpi_processor_get_info(struc
 	return 0;
 }
 
-static void *processor_device_array[NR_ACPI_CPUS];
+#ifndef CONFIG_XEN
+static void *processor_device_array[NR_CPUS];
+#else
+#include <linux/mutex.h>
+#include <linux/radix-tree.h>
+static DEFINE_MUTEX(processor_device_mutex);
+static RADIX_TREE(processor_device_tree, GFP_KERNEL);
+#endif
 
 static int acpi_processor_start(struct acpi_device *device)
 {
@@ -541,9 +548,20 @@ static int __cpuinit acpi_processor_add(
 	 * Don't trust it blindly
 	 */
 #ifdef CONFIG_XEN
-	BUG_ON(pr->acpi_id >= NR_ACPI_CPUS);
-	if (processor_device_array[pr->acpi_id] != NULL &&
-	    processor_device_array[pr->acpi_id] != (void *)device) {
+	mutex_lock(&processor_device_mutex);
+	result = radix_tree_insert(&processor_device_tree,
+				   pr->acpi_id, device);
+	switch (result) {
+	default:
+		goto end_unlock;
+	case -EEXIST:
+		if (radix_tree_lookup(&processor_device_tree,
+				      pr->acpi_id) == device) {
+	case 0:
+			mutex_unlock(&processor_device_mutex);
+			break;
+		}
+		mutex_unlock(&processor_device_mutex);
 #else
 	if (processor_device_array[pr->id] != NULL &&
 	    processor_device_array[pr->id] != (void *)device) {
@@ -553,14 +571,11 @@ static int __cpuinit acpi_processor_add(
 		return -ENODEV;
 	}
 #ifdef CONFIG_XEN
-	processor_device_array[pr->acpi_id] = (void *)device;
 	if (pr->id != -1)
-		processors[pr->id] = pr;
 #else
 	processor_device_array[pr->id] = (void *)device;
-
-	processors[pr->id] = pr;
 #endif /* CONFIG_XEN */
+	processors[pr->id] = pr;
 
 	result = acpi_processor_add_fs(device);
 	if (result)
@@ -602,6 +617,14 @@ err_thermal_unregister:
 	}
 
       end:
+#ifdef CONFIG_XEN
+	mutex_lock(&processor_device_mutex);
+	if (radix_tree_lookup(&processor_device_tree,
+			      pr->acpi_id) == device)
+		radix_tree_delete(&processor_device_tree, pr->acpi_id);
+      end_unlock:
+	mutex_unlock(&processor_device_mutex);
+#endif
 
 	return result;
 }
@@ -692,10 +715,8 @@ static int acpi_processor_remove(struct 
 
 #ifdef CONFIG_XEN
 	if (pr->id != -1)
-		processors[pr->id] = NULL;
-#else
+#endif
 	processors[pr->id] = NULL;
-#endif /* CONFIG_XEN */
 
 
 	kfree(pr);
@@ -992,6 +1013,30 @@ static void __exit acpi_processor_exit(v
 
 	remove_proc_entry(ACPI_PROCESSOR_CLASS, acpi_root_dir);
 
+#ifdef CONFIG_XEN
+	{
+		struct acpi_device *dev;
+		unsigned int idx = 0;
+
+		while (radix_tree_gang_lookup(&processor_device_tree,
+					      (void **)&dev, idx, 1)) {
+			struct acpi_processor *pr = acpi_driver_data(dev);
+
+			/* prevent live lock */
+			if (pr->acpi_id < idx) {
+				printk(KERN_WARNING PREFIX "ID %u unexpected"
+				       " (less than %u); leaking memory\n",
+				       pr->acpi_id, idx);
+				break;
+			}
+			idx = pr->acpi_id;
+			radix_tree_delete(&processor_device_tree, idx);
+			if (!++idx)
+				break;
+		}
+	}
+#endif
+
 	return;
 }
 
--- a/include/acpi/processor.h
+++ b/include/acpi/processor.h
@@ -24,12 +24,6 @@
 #define ACPI_TSD_REV0_REVISION		0	/* Support for _PSD as in ACPI 3.0 */
 #define ACPI_TSD_REV0_ENTRIES		5
 
-#ifdef CONFIG_XEN
-#define NR_ACPI_CPUS			(NR_CPUS < 256 ? 256 : NR_CPUS)
-#else
-#define NR_ACPI_CPUS			NR_CPUS
-#endif /* CONFIG_XEN */
-
 /*
  * Types of coordination defined in ACPI 3.0. Same macros can be used across
  * P, C and T states