ARC: [SMP] TLB flush

- Add mm_cpumask setting (aggregating only, unlike some other arches)
  used to restrict the TLB flush cross-calling

- cross-calling versions of TLB flush routines (thanks to Noam)

Signed-off-by: Noam Camus <noamc@ezchip.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

2 files changed, 25 insertions, 3 deletions

diff --git a/arch/arc/include/asm/mmu_context.h b/arch/arc/include/asm/mmu_context.h
index 45f06f566b02..1fd467ef658f 100644
--- a/arch/arc/include/asm/mmu_context.h
+++ b/arch/arc/include/asm/mmu_context.h
@@ -80,7 +80,7 @@ static inline void get_new_mmu_context(struct mm_struct *mm)
         /* move to new ASID and handle rollover */
         if (unlikely(!(++asid_cpu(cpu) & MM_CTXT_ASID_MASK))) {
 
-                flush_tlb_all();
+                local_flush_tlb_all();
 
                 /*
                  * Above checke for rollover of 8 bit ASID in 32 bit container.
@@ -131,6 +131,21 @@ static inline void destroy_context(struct mm_struct *mm)
 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
                              struct task_struct *tsk)
 {
+        const int cpu = smp_processor_id();
+
+        /*
+         * Note that the mm_cpumask is "aggregating" only, we don't clear it
+         * for the switched-out task, unlike some other arches.
+         * It is used to enlist cpus for sending TLB flush IPIs and not sending
+         * it to CPUs where a task once ran-on, could cause stale TLB entry
+         * re-use, specially for a multi-threaded task.
+         * e.g. T1 runs on C1, migrates to C3. T2 running on C2 munmaps.
+         *      For a non-aggregating mm_cpumask, IPI not sent C1, and if T1
+         *      were to re-migrate to C1, it could access the unmapped region
+         *      via any existing stale TLB entries.
+         */
+        cpumask_set_cpu(cpu, mm_cpumask(next));
+
 #ifndef CONFIG_SMP
         /* PGD cached in MMU reg to avoid 3 mem lookups: task->mm->pgd */
         write_aux_reg(ARC_REG_SCRATCH_DATA0, next->pgd);
diff --git a/arch/arc/include/asm/tlbflush.h b/arch/arc/include/asm/tlbflush.h
index b2f9bc7f68c8..71c7b2e4b874 100644
--- a/arch/arc/include/asm/tlbflush.h
+++ b/arch/arc/include/asm/tlbflush.h
@@ -18,11 +18,18 @@ void local_flush_tlb_kernel_range(unsigned long start, unsigned long end);
 void local_flush_tlb_range(struct vm_area_struct *vma,
                            unsigned long start, unsigned long end);
 
-/* XXX: Revisit for SMP */
+#ifndef CONFIG_SMP
 #define flush_tlb_range(vma, s, e)      local_flush_tlb_range(vma, s, e)
 #define flush_tlb_page(vma, page)       local_flush_tlb_page(vma, page)
 #define flush_tlb_kernel_range(s, e)    local_flush_tlb_kernel_range(s, e)
 #define flush_tlb_all()                 local_flush_tlb_all()
 #define flush_tlb_mm(mm)                local_flush_tlb_mm(mm)
-
+#else
+extern void flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
+                                                         unsigned long end);
+extern void flush_tlb_page(struct vm_area_struct *vma, unsigned long page);
+extern void flush_tlb_kernel_range(unsigned long start, unsigned long end);
+extern void flush_tlb_all(void);
+extern void flush_tlb_mm(struct mm_struct *mm);
+#endif /* CONFIG_SMP */
 #endif