powerpc/mm: Make switch_mm_irqs_off() out of line

It's too big to be inline, there is no reason to keep it
that way.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
[mpe: Rework to incorporate the comment changes via fixes branch]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 99 insertions, 0 deletions

diff --git a/arch/powerpc/mm/mmu_context.c b/arch/powerpc/mm/mmu_context.c
new file mode 100644
index 000000000000..0f613bc63c50
--- /dev/null
+++ b/arch/powerpc/mm/mmu_context.c
@@ -0,0 +1,99 @@
+/*
+ *  Common implementation of switch_mm_irqs_off
+ *
+ *  Copyright IBM Corp. 2017
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  as published by the Free Software Foundation; either version
+ *  2 of the License, or (at your option) any later version.
+ *
+ */
+
+#include <linux/mm.h>
+#include <linux/cpu.h>
+
+#include <asm/mmu_context.h>
+
+#if defined(CONFIG_PPC32)
+static inline void switch_mm_pgdir(struct task_struct *tsk,
+				   struct mm_struct *mm)
+{
+	/* 32-bit keeps track of the current PGDIR in the thread struct */
+	tsk->thread.pgdir = mm->pgd;
+}
+#elif defined(CONFIG_PPC_BOOK3E_64)
+static inline void switch_mm_pgdir(struct task_struct *tsk,
+				   struct mm_struct *mm)
+{
+	/* 64-bit Book3E keeps track of current PGD in the PACA */
+	get_paca()->pgd = mm->pgd;
+}
+#else
+static inline void switch_mm_pgdir(struct task_struct *tsk,
+				   struct mm_struct *mm) { }
+#endif
+
+#ifdef CONFIG_PPC_BOOK3S_64
+static inline void inc_mm_active_cpus(struct mm_struct *mm)
+{
+	atomic_inc(&mm->context.active_cpus);
+}
+#else
+static inline void inc_mm_active_cpus(struct mm_struct *mm) { }
+#endif
+
+void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
+			struct task_struct *tsk)
+{
+	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));
+		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.
+		 *
+		 * 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().
+		 *
+		 * On the read side the barrier is in pte_xchg(), which orders
+		 * the store to the PTE vs the load of mm_cpumask.
+		 */
+		smp_mb();
+
+		new_on_cpu = true;
+	}
+
+	/* Some subarchs need to track the PGD elsewhere */
+	switch_mm_pgdir(tsk, next);
+
+	/* Nothing else to do if we aren't actually switching */
+	if (prev == next)
+		return;
+
+	/*
+	 * We must stop all altivec streams before changing the HW
+	 * context
+	 */
+	if (cpu_has_feature(CPU_FTR_ALTIVEC))
+		asm volatile ("dssall");
+
+	if (new_on_cpu)
+		radix_kvm_prefetch_workaround(next);
+
+	/*
+	 * The actual HW switching method differs between the various
+	 * sub architectures. Out of line for now
+	 */
+	switch_mmu_context(prev, next, tsk);
+}
+