1 files changed, 25 insertions, 23 deletions

diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c
index 4a0544492f1..6eb97b3a748 100644
--- a/arch/arm/mm/context.c
+++ b/arch/arm/mm/context.c
@@ -36,8 +36,8 @@
  * The context ID is used by debuggers and trace logic, and
  * should be unique within all running processes.
  *
- * In big endian operation, the two 32 bit words are swapped if accesed by
- * non 64-bit operations.
+ * In big endian operation, the two 32 bit words are swapped if accessed
+ * by non-64-bit operations.
  */
 #define ASID_FIRST_VERSION	(1ULL << ASID_BITS)
 #define NUM_USER_ASIDS		ASID_FIRST_VERSION
@@ -78,20 +78,21 @@ void a15_erratum_get_cpumask(int this_cpu, struct mm_struct *mm,
 #endif
 
 #ifdef CONFIG_ARM_LPAE
-static void cpu_set_reserved_ttbr0(void)
-{
-	/*
-	 * Set TTBR0 to swapper_pg_dir which contains only global entries. The
-	 * ASID is set to 0.
-	 */
-	cpu_set_ttbr(0, __pa(swapper_pg_dir));
-	isb();
-}
+/*
+ * With LPAE, the ASID and page tables are updated atomicly, so there is
+ * no need for a reserved set of tables (the active ASID tracking prevents
+ * any issues across a rollover).
+ */
+#define cpu_set_reserved_ttbr0()
 #else
 static void cpu_set_reserved_ttbr0(void)
 {
 	u32 ttb;
-	/* Copy TTBR1 into TTBR0 */
+	/*
+	 * Copy TTBR1 into TTBR0.
+	 * This points at swapper_pg_dir, which contains only global
+	 * entries so any speculative walks are perfectly safe.
+	 */
 	asm volatile(
 	"	mrc	p15, 0, %0, c2, c0, 1		@ read TTBR1\n"
 	"	mcr	p15, 0, %0, c2, c0, 0		@ set TTBR0\n"
@@ -162,10 +163,7 @@ static void flush_context(unsigned int cpu)
 	}
 
 	/* Queue a TLB invalidate and flush the I-cache if necessary. */
-	if (!tlb_ops_need_broadcast())
-		cpumask_set_cpu(cpu, &tlb_flush_pending);
-	else
-		cpumask_setall(&tlb_flush_pending);
+	cpumask_setall(&tlb_flush_pending);
 
 	if (icache_is_vivt_asid_tagged())
 		__flush_icache_all();
@@ -182,6 +180,7 @@ static int is_reserved_asid(u64 asid)
 
 static u64 new_context(struct mm_struct *mm, unsigned int cpu)
 {
+	static u32 cur_idx = 1;
 	u64 asid = atomic64_read(&mm->context.id);
 	u64 generation = atomic64_read(&asid_generation);
 
@@ -196,10 +195,13 @@ static u64 new_context(struct mm_struct *mm, unsigned int cpu)
 		 * Allocate a free ASID. If we can't find one, take a
 		 * note of the currently active ASIDs and mark the TLBs
 		 * as requiring flushes. We always count from ASID #1,
-		 * as we reserve ASID #0 to switch via TTBR0 and indicate
-		 * rollover events.
+		 * as we reserve ASID #0 to switch via TTBR0 and to
+		 * avoid speculative page table walks from hitting in
+		 * any partial walk caches, which could be populated
+		 * from overlapping level-1 descriptors used to map both
+		 * the module area and the userspace stack.
 		 */
-		asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, 1);
+		asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, cur_idx);
 		if (asid == NUM_USER_ASIDS) {
 			generation = atomic64_add_return(ASID_FIRST_VERSION,
 							 &asid_generation);
@@ -207,6 +209,7 @@ static u64 new_context(struct mm_struct *mm, unsigned int cpu)
 			asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, 1);
 		}
 		__set_bit(asid, asid_map);
+		cur_idx = asid;
 		asid |= generation;
 		cpumask_clear(mm_cpumask(mm));
 	}
@@ -224,8 +227,9 @@ void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk)
 		__check_vmalloc_seq(mm);
 
 	/*
-	 * Required during context switch to avoid speculative page table
-	 * walking with the wrong TTBR.
+	 * We cannot update the pgd and the ASID atomicly with classic
+	 * MMU, so switch exclusively to global mappings to avoid
+	 * speculative page table walking with the wrong TTBR.
 	 */
 	cpu_set_reserved_ttbr0();
 
@@ -245,8 +249,6 @@ void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk)
 	if (cpumask_test_and_clear_cpu(cpu, &tlb_flush_pending)) {
 		local_flush_bp_all();
 		local_flush_tlb_all();
-		if (erratum_a15_798181())
-			dummy_flush_tlb_a15_erratum();
 	}
 
 	atomic64_set(&per_cpu(active_asids, cpu), asid);