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authorChristophe Leroy <christophe.leroy@c-s.fr>2019-03-29 10:00:01 +0000
committerMichael Ellerman <mpe@ellerman.id.au>2019-05-03 01:20:22 +1000
commit17312f258cf6eb584f276ad592972ade7e16e318 (patch)
tree760470f840e1de714cac95f9b948231930764418 /arch/powerpc/mm/book3s32/mmu_context.c
parent47d99948eee48a84a4b242c17915a4ff59a29b5d (diff)
powerpc/mm: Move book3s32 specifics in subdirectory mm/book3s64
Several files in arch/powerpc/mm are only for book3S32. This patch creates a subdirectory for them. Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> [mpe: Shorten new filenames] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/mm/book3s32/mmu_context.c')
-rw-r--r--arch/powerpc/mm/book3s32/mmu_context.c118
1 files changed, 118 insertions, 0 deletions
diff --git a/arch/powerpc/mm/book3s32/mmu_context.c b/arch/powerpc/mm/book3s32/mmu_context.c
new file mode 100644
index 000000000000..921c1e33e941
--- /dev/null
+++ b/arch/powerpc/mm/book3s32/mmu_context.c
@@ -0,0 +1,118 @@
+/*
+ * This file contains the routines for handling the MMU on those
+ * PowerPC implementations where the MMU substantially follows the
+ * architecture specification. This includes the 6xx, 7xx, 7xxx,
+ * and 8260 implementations but excludes the 8xx and 4xx.
+ * -- paulus
+ *
+ * Derived from arch/ppc/mm/init.c:
+ * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
+ *
+ * Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
+ * and Cort Dougan (PReP) (cort@cs.nmt.edu)
+ * Copyright (C) 1996 Paul Mackerras
+ *
+ * Derived from "arch/i386/mm/init.c"
+ * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
+ *
+ * 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/init.h>
+#include <linux/export.h>
+
+#include <asm/mmu_context.h>
+
+/*
+ * On 32-bit PowerPC 6xx/7xx/7xxx CPUs, we use a set of 16 VSIDs
+ * (virtual segment identifiers) for each context. Although the
+ * hardware supports 24-bit VSIDs, and thus >1 million contexts,
+ * we only use 32,768 of them. That is ample, since there can be
+ * at most around 30,000 tasks in the system anyway, and it means
+ * that we can use a bitmap to indicate which contexts are in use.
+ * Using a bitmap means that we entirely avoid all of the problems
+ * that we used to have when the context number overflowed,
+ * particularly on SMP systems.
+ * -- paulus.
+ */
+#define NO_CONTEXT ((unsigned long) -1)
+#define LAST_CONTEXT 32767
+#define FIRST_CONTEXT 1
+
+/*
+ * This function defines the mapping from contexts to VSIDs (virtual
+ * segment IDs). We use a skew on both the context and the high 4 bits
+ * of the 32-bit virtual address (the "effective segment ID") in order
+ * to spread out the entries in the MMU hash table. Note, if this
+ * function is changed then arch/ppc/mm/hashtable.S will have to be
+ * changed to correspond.
+ *
+ *
+ * CTX_TO_VSID(ctx, va) (((ctx) * (897 * 16) + ((va) >> 28) * 0x111) \
+ * & 0xffffff)
+ */
+
+static unsigned long next_mmu_context;
+static unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1];
+
+unsigned long __init_new_context(void)
+{
+ unsigned long ctx = next_mmu_context;
+
+ while (test_and_set_bit(ctx, context_map)) {
+ ctx = find_next_zero_bit(context_map, LAST_CONTEXT+1, ctx);
+ if (ctx > LAST_CONTEXT)
+ ctx = 0;
+ }
+ next_mmu_context = (ctx + 1) & LAST_CONTEXT;
+
+ return ctx;
+}
+EXPORT_SYMBOL_GPL(__init_new_context);
+
+/*
+ * Set up the context for a new address space.
+ */
+int init_new_context(struct task_struct *t, struct mm_struct *mm)
+{
+ mm->context.id = __init_new_context();
+
+ return 0;
+}
+
+/*
+ * Free a context ID. Make sure to call this with preempt disabled!
+ */
+void __destroy_context(unsigned long ctx)
+{
+ clear_bit(ctx, context_map);
+}
+EXPORT_SYMBOL_GPL(__destroy_context);
+
+/*
+ * We're finished using the context for an address space.
+ */
+void destroy_context(struct mm_struct *mm)
+{
+ preempt_disable();
+ if (mm->context.id != NO_CONTEXT) {
+ __destroy_context(mm->context.id);
+ mm->context.id = NO_CONTEXT;
+ }
+ preempt_enable();
+}
+
+/*
+ * Initialize the context management stuff.
+ */
+void __init mmu_context_init(void)
+{
+ /* Reserve context 0 for kernel use */
+ context_map[0] = (1 << FIRST_CONTEXT) - 1;
+ next_mmu_context = FIRST_CONTEXT;
+}