[1/3] riscv: move switch_mm to its own file

Commit Message

Gary Guo March 7, 2019, 1:26 a.m. UTC

switch_mm is an expensive operations that has two users.
flush_icache_deferred is only called within switch_mm and can be moved
together. The function is expected to be more complicated when ASID
support is added, so clean up eagerly.

By moving them to a separate file we also removes some excessive
dependency of tlbflush.h and cacheflush.h.

Signed-off-by: Xuan Guo <[e-mail]>
---
 arch/riscv/include/asm/mmu_context.h | 59 +-------------------
 arch/riscv/mm/Makefile               |  1 +
 arch/riscv/mm/context.c              | 83 ++++++++++++++++++++++++++++
 3 files changed, 86 insertions(+), 57 deletions(-)
 create mode 100644 arch/riscv/mm/context.c

Comments

Christoph Hellwig March 8, 2019, 2:27 p.m. UTC | #1

> +extern void switch_mm(struct mm_struct *prev, struct mm_struct *next,
> +		struct task_struct *task);

No need for the extern here.

> diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c
> new file mode 100644
> index 000000000000..4b9a20135008
> --- /dev/null
> +++ b/arch/riscv/mm/context.c
> @@ -0,0 +1,83 @@
> +/*
> + * Copyright (C) 2012 Regents of the University of California
> + * Copyright (C) 2017 SiFive
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> + */

Please use an SPDX tag instead of the copyright boilerplate for new
files.

> +static inline void flush_icache_deferred(struct mm_struct *mm)
> +{
> +#ifdef CONFIG_SMP
> +	unsigned int cpu = smp_processor_id();
> +	cpumask_t *mask = &mm->context.icache_stale_mask;
> +
> +	if (cpumask_test_cpu(cpu, mask)) {
> +		cpumask_clear_cpu(cpu, mask);
> +		/*
> +		 * Ensure the remote hart's writes are visible to this hart.
> +		 * This pairs with a barrier in flush_icache_mm.
> +		 */
> +		smp_mb();
> +		local_flush_icache_all();
> +	}
> +
> +#endif
> +}
> +
> +void switch_mm(struct mm_struct *prev,
> +	struct mm_struct *next, struct task_struct *task)

The second argument easily fits on the previous line.

Patch

diff --git a/arch/riscv/include/asm/mmu_context.h b/arch/riscv/include/asm/mmu_context.h
index 336d60ec5698..c595552cb6bf 100644
--- a/arch/riscv/include/asm/mmu_context.h
+++ b/arch/riscv/include/asm/mmu_context.h
@@ -20,8 +20,6 @@ 
 
 #include <linux/mm.h>
 #include <linux/sched.h>
-#include <asm/tlbflush.h>
-#include <asm/cacheflush.h>
 
 static inline void enter_lazy_tlb(struct mm_struct *mm,
 	struct task_struct *task)
@@ -39,61 +37,8 @@  static inline void destroy_context(struct mm_struct *mm)
 {
 }
 
-/*
- * When necessary, performs a deferred icache flush for the given MM context,
- * on the local CPU.  RISC-V has no direct mechanism for instruction cache
- * shoot downs, so instead we send an IPI that informs the remote harts they
- * need to flush their local instruction caches.  To avoid pathologically slow
- * behavior in a common case (a bunch of single-hart processes on a many-hart
- * machine, ie 'make -j') we avoid the IPIs for harts that are not currently
- * executing a MM context and instead schedule a deferred local instruction
- * cache flush to be performed before execution resumes on each hart.  This
- * actually performs that local instruction cache flush, which implicitly only
- * refers to the current hart.
- */
-static inline void flush_icache_deferred(struct mm_struct *mm)
-{
-#ifdef CONFIG_SMP
-	unsigned int cpu = smp_processor_id();
-	cpumask_t *mask = &mm->context.icache_stale_mask;
-
-	if (cpumask_test_cpu(cpu, mask)) {
-		cpumask_clear_cpu(cpu, mask);
-		/*
-		 * Ensure the remote hart's writes are visible to this hart.
-		 * This pairs with a barrier in flush_icache_mm.
-		 */
-		smp_mb();
-		local_flush_icache_all();
-	}
-#endif
-}
-
-static inline void switch_mm(struct mm_struct *prev,
-	struct mm_struct *next, struct task_struct *task)
-{
-	if (likely(prev != next)) {
-		/*
-		 * Mark the current MM context as inactive, and the next as
-		 * active.  This is at least used by the icache flushing
-		 * routines in order to determine who should
-		 */
-		unsigned int cpu = smp_processor_id();
-
-		cpumask_clear_cpu(cpu, mm_cpumask(prev));
-		cpumask_set_cpu(cpu, mm_cpumask(next));
-
-		/*
-		 * Use the old spbtr name instead of using the current satp
-		 * name to support binutils 2.29 which doesn't know about the
-		 * privileged ISA 1.10 yet.
-		 */
-		csr_write(sptbr, virt_to_pfn(next->pgd) | SATP_MODE);
-		local_flush_tlb_all();
-
-		flush_icache_deferred(next);
-	}
-}
+extern void switch_mm(struct mm_struct *prev, struct mm_struct *next,
+		struct task_struct *task);
 
 static inline void activate_mm(struct mm_struct *prev,
 			       struct mm_struct *next)
diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
index eb22ab49b3e0..d75b035786d6 100644
--- a/arch/riscv/mm/Makefile
+++ b/arch/riscv/mm/Makefile
@@ -3,3 +3,4 @@  obj-y += fault.o
 obj-y += extable.o
 obj-y += ioremap.o
 obj-y += cacheflush.o
+obj-y += context.o
diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c
new file mode 100644
index 000000000000..4b9a20135008
--- /dev/null
+++ b/arch/riscv/mm/context.c
@@ -0,0 +1,83 @@ 
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ * Copyright (C) 2017 SiFive
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/mm.h>
+
+#include <asm/tlbflush.h>
+#include <asm/cacheflush.h>
+
+/*
+ * When necessary, performs a deferred icache flush for the given MM context,
+ * on the local CPU.  RISC-V has no direct mechanism for instruction cache
+ * shoot downs, so instead we send an IPI that informs the remote harts they
+ * need to flush their local instruction caches.  To avoid pathologically slow
+ * behavior in a common case (a bunch of single-hart processes on a many-hart
+ * machine, ie 'make -j') we avoid the IPIs for harts that are not currently
+ * executing a MM context and instead schedule a deferred local instruction
+ * cache flush to be performed before execution resumes on each hart.  This
+ * actually performs that local instruction cache flush, which implicitly only
+ * refers to the current hart.
+ */
+static inline void flush_icache_deferred(struct mm_struct *mm)
+{
+#ifdef CONFIG_SMP
+	unsigned int cpu = smp_processor_id();
+	cpumask_t *mask = &mm->context.icache_stale_mask;
+
+	if (cpumask_test_cpu(cpu, mask)) {
+		cpumask_clear_cpu(cpu, mask);
+		/*
+		 * Ensure the remote hart's writes are visible to this hart.
+		 * This pairs with a barrier in flush_icache_mm.
+		 */
+		smp_mb();
+		local_flush_icache_all();
+	}
+
+#endif
+}
+
+void switch_mm(struct mm_struct *prev,
+	struct mm_struct *next, struct task_struct *task)
+{
+	unsigned int cpu;
+
+	if (unlikely(prev == next))
+		return;
+
+	/*
+	 * Mark the current MM context as inactive, and the next as
+	 * active.  This is at least used by the icache flushing
+	 * routines in order to determine who should be flushed.
+	 */
+	cpu = smp_processor_id();
+
+	cpumask_clear_cpu(cpu, mm_cpumask(prev));
+	cpumask_set_cpu(cpu, mm_cpumask(next));
+
+	/*
+	 * Use the old spbtr name instead of using the current satp
+	 * name to support binutils 2.29 which doesn't know about the
+	 * privileged ISA 1.10 yet.
+	 */
+	csr_write(sptbr, virt_to_pfn(next->pgd) | SATP_MODE);
+	local_flush_tlb_all();
+
+	flush_icache_deferred(next);
+}
+
+