[ARM] Add ARMv6 MMU context handling.

Add MMU context ID handling.

arch/arm/mm/mmu.c

+/*
+ *  linux/arch/arm/mm/mmu.c
+ *
+ *  Copyright (C) 2002-2003 Deep Blue Solutions Ltd, all rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+
+#include <asm/mmu_context.h>
+#include <asm/pgalloc.h>
+#include <asm/tlbflush.h>
+
+unsigned int cpu_last_asid = { 1 << ASID_BITS };
+
+/*
+ * We fork()ed a process, and we need a new context for the child
+ * to run in.  We reserve version 0 for initial tasks so we will
+ * always allocate an ASID.
+ */
+void __init_new_context(struct task_struct *tsk, struct mm_struct *mm)
+{
+	mm->context.id = 0;
+}
+
+void __new_context(struct mm_struct *mm)
+{
+	unsigned int asid;
+
+	asid = ++cpu_last_asid;
+	if (asid == 0)
+		asid = cpu_last_asid = 1 << ASID_BITS;
+
+	/*
+	 * If we've used up all our ASIDs, we need
+	 * to start a new version and flush the TLB.
+	 */
+	if ((asid & ~ASID_MASK) == 0)
+		flush_tlb_all();
+
+	mm->context.id = asid;
+}

include/asm-arm/mmu.h

 #ifndef __ARM_MMU_H
 #define __ARM_MMU_H
 
-/*
- * The ARM doesn't have a mmu context
- */
-typedef struct { } mm_context_t;
+#include <linux/config.h>
+
+typedef struct {
+#if __LINUX_ARM_ARCH__ >= 6
+	unsigned int id;
+#endif
+} mm_context_t;
+
+#if __LINUX_ARM_ARCH__ >= 6
+#define ASID(mm)	((mm)->context.id & 255)
+#else
+#define ASID(mm)	(0)
+#endif
 
 #endif

include/asm-arm/mmu_context.h

@@ -15,7 +15,45 @@
 
 #include <asm/proc-fns.h>
 
+#if __LINUX_ARM_ARCH__ >= 6
+
+/*
+ * On ARMv6, we have the following structure in the Context ID:
+ *
+ * 31                         7          0
+ * +-------------------------+-----------+
+ * |      process ID         |   ASID    |
+ * +-------------------------+-----------+
+ * |              context ID             |
+ * +-------------------------------------+
+ *
+ * The ASID is used to tag entries in the CPU caches and TLBs.
+ * The context ID is used by debuggers and trace logic, and
+ * should be unique within all running processes.
+ */
+#define ASID_BITS	8
+#define ASID_MASK	((~0) << ASID_BITS)
+
+extern unsigned int cpu_last_asid;
+
+void __init_new_context(struct task_struct *tsk, struct mm_struct *mm);
+void __new_context(struct mm_struct *mm);
+
+static inline void check_context(struct mm_struct *mm)
+{
+	if (unlikely((mm->context.id ^ cpu_last_asid) >> ASID_BITS))
+		__new_context(mm);
+}
+
+#define init_new_context(tsk,mm)	(__init_new_context(tsk,mm),0)
+
+#else
+
+#define check_context(mm)		do { } while (0)
 #define init_new_context(tsk,mm)	0
+
+#endif
+
 #define destroy_context(mm)		do { } while(0)
 
 /*
@@ -43,6 +81,7 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next,
 	  struct task_struct *tsk)
 {
 	if (prev != next) {
+		check_context(next);
 		cpu_switch_mm(next->pgd, next);
 	}
 }
@@ -51,6 +90,7 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next,
 
 static inline void activate_mm(struct mm_struct *prev, struct mm_struct *next)
 {
+	check_context(next);
 	cpu_switch_mm(next->pgd, next);
 }