+ /*
+ * The MPC8xx has only 16 contexts. We rotate through them on each
+ * task switch. A better way would be to keep track of tasks that
+ * own contexts, and implement an LRU usage. That way very active
+ * tasks don't always have to pay the TLB reload overhead. The
+ * kernel pages are mapped shared, so the kernel can run on behalf
+ * of any task that makes a kernel entry. Shared does not mean they
+ * are not protected, just that the ASID comparison is not performed.
+ * -- Dan
+ *
+ * The IBM4xx has 256 contexts, so we can just rotate through these
+ * as a way of "switching" contexts. If the TID of the TLB is zero,
+ * the PID/TID comparison is disabled, so we can use a TID of zero
+ * to represent all kernel pages as shared among all contexts.
+ * -- Dan
+ */
+ if (mmu_has_feature(MMU_FTR_TYPE_8xx)) {
+ first_context = 0;
+ last_context = 15;
+ } else {
+ first_context = 1;
+ last_context = 255;
+ }
+
+#ifdef DEBUG_CLAMP_LAST_CONTEXT
+ last_context = DEBUG_CLAMP_LAST_CONTEXT;
+#endif
+ /*
+ * Allocate the maps used by context management
+ */
+ context_map = alloc_bootmem(CTX_MAP_SIZE);
+ context_mm = alloc_bootmem(sizeof(void *) * (last_context + 1));
+ stale_map[0] = alloc_bootmem(CTX_MAP_SIZE);
+
+#ifdef CONFIG_SMP
+ register_cpu_notifier(&mmu_context_cpu_nb);
+#endif
+
+ printk(KERN_INFO
+ "MMU: Allocated %d bytes of context maps for %d contexts\n",
+ 2 * CTX_MAP_SIZE + (sizeof(void *) * (last_context + 1)),
+ last_context - first_context + 1);
+