ARC: [SMP] ASID allocation

-Track a Per CPU ASID counter
-mm-per-cpu ASID (multiple threads, or mm migrated around)

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

2 files changed, 29 insertions, 17 deletions

diff --git a/arch/arc/include/asm/mmu.h b/arch/arc/include/asm/mmu.h
index c2663b32866..8c84ae98c33 100644
--- a/arch/arc/include/asm/mmu.h
+++ b/arch/arc/include/asm/mmu.h
@@ -48,7 +48,7 @@
 #ifndef __ASSEMBLY__
 
 typedef struct {
-	unsigned long asid;	/* 8 bit MMU PID + Generation cycle */
+	unsigned long asid[NR_CPUS];	/* 8 bit MMU PID + Generation cycle */
 } mm_context_t;
 
 #ifdef CONFIG_ARC_DBG_TLB_PARANOIA
diff --git a/arch/arc/include/asm/mmu_context.h b/arch/arc/include/asm/mmu_context.h
index 43a1b51bb8c..45f06f566b0 100644
--- a/arch/arc/include/asm/mmu_context.h
+++ b/arch/arc/include/asm/mmu_context.h
@@ -30,13 +30,13 @@
  * "Fast Context Switch" i.e. no TLB flush on ctxt-switch
  *
  * Linux assigns each task a unique ASID. A simple round-robin allocation
- * of H/w ASID is done using software tracker @asid_cache.
+ * of H/w ASID is done using software tracker @asid_cpu.
  * When it reaches max 255, the allocation cycle starts afresh by flushing
  * the entire TLB and wrapping ASID back to zero.
  *
  * A new allocation cycle, post rollover, could potentially reassign an ASID
  * to a different task. Thus the rule is to refresh the ASID in a new cycle.
- * The 32 bit @asid_cache (and mm->asid) have 8 bits MMU PID and rest 24 bits
+ * The 32 bit @asid_cpu (and mm->asid) have 8 bits MMU PID and rest 24 bits
  * serve as cycle/generation indicator and natural 32 bit unsigned math
  * automagically increments the generation when lower 8 bits rollover.
  */
@@ -47,9 +47,11 @@
 #define MM_CTXT_FIRST_CYCLE	(MM_CTXT_ASID_MASK + 1)
 #define MM_CTXT_NO_ASID		0UL
 
-#define hw_pid(mm)		(mm->context.asid & MM_CTXT_ASID_MASK)
+#define asid_mm(mm, cpu)	mm->context.asid[cpu]
+#define hw_pid(mm, cpu)		(asid_mm(mm, cpu) & MM_CTXT_ASID_MASK)
 
-extern unsigned int asid_cache;
+DECLARE_PER_CPU(unsigned int, asid_cache);
+#define asid_cpu(cpu)		per_cpu(asid_cache, cpu)
 
 /*
  * Get a new ASID if task doesn't have a valid one (unalloc or from prev cycle)
@@ -57,6 +59,7 @@ extern unsigned int asid_cache;
  */
 static inline void get_new_mmu_context(struct mm_struct *mm)
 {
+	const unsigned int cpu = smp_processor_id();
 	unsigned long flags;
 
 	local_irq_save(flags);
@@ -71,11 +74,11 @@ static inline void get_new_mmu_context(struct mm_struct *mm)
 	 * 	 first need to destroy the context, setting it to invalid
 	 * 	 value.
 	 */
-	if (!((mm->context.asid ^ asid_cache) & MM_CTXT_CYCLE_MASK))
+	if (!((asid_mm(mm, cpu) ^ asid_cpu(cpu)) & MM_CTXT_CYCLE_MASK))
 		goto set_hw;
 
 	/* move to new ASID and handle rollover */
-	if (unlikely(!(++asid_cache & MM_CTXT_ASID_MASK))) {
+	if (unlikely(!(++asid_cpu(cpu) & MM_CTXT_ASID_MASK))) {
 
 		flush_tlb_all();
 
@@ -84,15 +87,15 @@ static inline void get_new_mmu_context(struct mm_struct *mm)
 		 * If the container itself wrapped around, set it to a non zero
 		 * "generation" to distinguish from no context
 		 */
-		if (!asid_cache)
-			asid_cache = MM_CTXT_FIRST_CYCLE;
+		if (!asid_cpu(cpu))
+			asid_cpu(cpu) = MM_CTXT_FIRST_CYCLE;
 	}
 
 	/* Assign new ASID to tsk */
-	mm->context.asid = asid_cache;
+	asid_mm(mm, cpu) = asid_cpu(cpu);
 
 set_hw:
-	write_aux_reg(ARC_REG_PID, hw_pid(mm) | MMU_ENABLE);
+	write_aux_reg(ARC_REG_PID, hw_pid(mm, cpu) | MMU_ENABLE);
 
 	local_irq_restore(flags);
 }
@@ -104,10 +107,24 @@ set_hw:
 static inline int
 init_new_context(struct task_struct *tsk, struct mm_struct *mm)
 {
-	mm->context.asid = MM_CTXT_NO_ASID;
+	int i;
+
+	for_each_possible_cpu(i)
+		asid_mm(mm, i) = MM_CTXT_NO_ASID;
+
 	return 0;
 }
 
+static inline void destroy_context(struct mm_struct *mm)
+{
+	unsigned long flags;
+
+	/* Needed to elide CONFIG_DEBUG_PREEMPT warning */
+	local_irq_save(flags);
+	asid_mm(mm, smp_processor_id()) = MM_CTXT_NO_ASID;
+	local_irq_restore(flags);
+}
+
 /* Prepare the MMU for task: setup PID reg with allocated ASID
     If task doesn't have an ASID (never alloc or stolen, get a new ASID)
 */
@@ -131,11 +148,6 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
  */
 #define activate_mm(prev, next)		switch_mm(prev, next, NULL)
 
-static inline void destroy_context(struct mm_struct *mm)
-{
-	mm->context.asid = MM_CTXT_NO_ASID;
-}
-
 /* it seemed that deactivate_mm( ) is a reasonable place to do book-keeping
  * for retiring-mm. However destroy_context( ) still needs to do that because
  * between mm_release( ) = >deactive_mm( ) and