1 files changed, 30 insertions, 17 deletions

diff --git a/arch/powerpc/mm/mmu_context.c b/arch/powerpc/mm/mmu_context.c
index 18f20da0d348..b24c19078eb1 100644
--- a/arch/powerpc/mm/mmu_context.c
+++ b/arch/powerpc/mm/mmu_context.c
@@ -18,6 +18,12 @@ static inline void switch_mm_pgdir(struct task_struct *tsk,
 {
 	/* 32-bit keeps track of the current PGDIR in the thread struct */
 	tsk->thread.pgdir = mm->pgd;
+#ifdef CONFIG_PPC_BOOK3S_32
+	tsk->thread.sr0 = mm->context.sr0;
+#endif
+#if defined(CONFIG_BOOKE_OR_40x) && defined(CONFIG_PPC_KUAP)
+	tsk->thread.pid = mm->context.id;
+#endif
 }
 #elif defined(CONFIG_PPC_BOOK3E_64)
 static inline void switch_mm_pgdir(struct task_struct *tsk,
@@ -25,6 +31,9 @@ static inline void switch_mm_pgdir(struct task_struct *tsk,
 {
 	/* 64-bit Book3E keeps track of current PGD in the PACA */
 	get_paca()->pgd = mm->pgd;
+#ifdef CONFIG_PPC_KUAP
+	tsk->thread.pid = mm->context.id;
+#endif
 }
 #else
 static inline void switch_mm_pgdir(struct task_struct *tsk,
@@ -34,33 +43,37 @@ static inline void switch_mm_pgdir(struct task_struct *tsk,
 void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 			struct task_struct *tsk)
 {
+	int cpu = smp_processor_id();
 	bool new_on_cpu = false;
 
 	/* Mark this context has been used on the new CPU */
-	if (!cpumask_test_cpu(smp_processor_id(), mm_cpumask(next))) {
-		cpumask_set_cpu(smp_processor_id(), mm_cpumask(next));
+	if (!cpumask_test_cpu(cpu, mm_cpumask(next))) {
+		VM_WARN_ON_ONCE(next == &init_mm);
+		cpumask_set_cpu(cpu, mm_cpumask(next));
 		inc_mm_active_cpus(next);
 
 		/*
 		 * This full barrier orders the store to the cpumask above vs
-		 * a subsequent operation which allows this CPU to begin loading
-		 * translations for next.
+		 * a subsequent load which allows this CPU/MMU to begin loading
+		 * translations for 'next' from page table PTEs into the TLB.
 		 *
-		 * When using the radix MMU that operation is the load of the
+		 * When using the radix MMU, that operation is the load of the
 		 * MMU context id, which is then moved to SPRN_PID.
 		 *
 		 * For the hash MMU it is either the first load from slb_cache
-		 * in switch_slb(), and/or the store of paca->mm_ctx_id in
-		 * copy_mm_to_paca().
+		 * in switch_slb() to preload the SLBs, or the load of
+		 * get_user_context which loads the context for the VSID hash
+		 * to insert a new SLB, in the SLB fault handler.
 		 *
 		 * On the other side, the barrier is in mm/tlb-radix.c for
-		 * radix which orders earlier stores to clear the PTEs vs
-		 * the load of mm_cpumask. And pte_xchg which does the same
-		 * thing for hash.
+		 * radix which orders earlier stores to clear the PTEs before
+		 * the load of mm_cpumask to check which CPU TLBs should be
+		 * flushed. For hash, pte_xchg to clear the PTE includes the
+		 * barrier.
 		 *
-		 * This full barrier is needed by membarrier when switching
-		 * between processes after store to rq->curr, before user-space
-		 * memory accesses.
+		 * This full barrier is also needed by membarrier when
+		 * switching between processes after store to rq->curr, before
+		 * user-space memory accesses.
 		 */
 		smp_mb();
 
@@ -79,11 +92,9 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 	 * context
 	 */
 	if (cpu_has_feature(CPU_FTR_ALTIVEC))
-		asm volatile ("dssall");
+		asm volatile (PPC_DSSALL);
 
-	if (new_on_cpu)
-		radix_kvm_prefetch_workaround(next);
-	else
+	if (!new_on_cpu)
 		membarrier_arch_switch_mm(prev, next, tsk);
 
 	/*
@@ -91,6 +102,8 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 	 * sub architectures. Out of line for now
 	 */
 	switch_mmu_context(prev, next, tsk);
+
+	VM_WARN_ON_ONCE(!cpumask_test_cpu(cpu, mm_cpumask(prev)));
 }
 
 #ifndef CONFIG_PPC_BOOK3S_64