[PATCH 5/9] powerpc: Split mmu_context handling
Benjamin Herrenschmidt
benh at kernel.crashing.org
Mon Dec 8 16:40:38 EST 2008
This splits the mmu_context handling between 32-bit hash based processors,
64-bit hash based processors and everybody else. This is preliminary work
for adding SMP support for BookE processors.
Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
---
arch/powerpc/include/asm/mmu_context.h | 260 +++------------------------
arch/powerpc/kernel/asm-offsets.c | 1
arch/powerpc/kernel/head_32.S | 12 +
arch/powerpc/kernel/ppc_ksyms.c | 3
arch/powerpc/kernel/swsusp.c | 2
arch/powerpc/mm/Makefile | 7
arch/powerpc/mm/mmu_context_hash32.c | 103 ++++++++++
arch/powerpc/mm/mmu_context_hash64.c | 78 ++++++++
arch/powerpc/mm/mmu_context_nohash.c | 162 ++++++++++++++++
arch/powerpc/platforms/Kconfig.cputype | 10 -
arch/powerpc/platforms/powermac/cpufreq_32.c | 2
drivers/macintosh/via-pmu.c | 4
12 files changed, 407 insertions(+), 237 deletions(-)
--- linux-work.orig/arch/powerpc/include/asm/mmu_context.h 2008-12-08 14:37:13.000000000 +1100
+++ linux-work/arch/powerpc/include/asm/mmu_context.h 2008-12-08 14:45:47.000000000 +1100
@@ -2,240 +2,26 @@
#define __ASM_POWERPC_MMU_CONTEXT_H
#ifdef __KERNEL__
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
#include <asm/mmu.h>
#include <asm/cputable.h>
#include <asm-generic/mm_hooks.h>
-
-#ifndef CONFIG_PPC64
-#include <asm/atomic.h>
-#include <linux/bitops.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.
- */
-
-/*
- * 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.
- */
-#define CTX_TO_VSID(ctx, va) (((ctx) * (897 * 16) + ((va) >> 28) * 0x111) \
- & 0xffffff)
-
-/*
- The MPC8xx has only 16 contexts. We rotate through them on each
- task switch. A better way would be to keep track of tasks that
- own contexts, and implement an LRU usage. That way very active
- tasks don't always have to pay the TLB reload overhead. The
- kernel pages are mapped shared, so the kernel can run on behalf
- of any task that makes a kernel entry. Shared does not mean they
- are not protected, just that the ASID comparison is not performed.
- -- Dan
-
- The IBM4xx has 256 contexts, so we can just rotate through these
- as a way of "switching" contexts. If the TID of the TLB is zero,
- the PID/TID comparison is disabled, so we can use a TID of zero
- to represent all kernel pages as shared among all contexts.
- -- Dan
- */
-
-static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
-{
-}
-
-#ifdef CONFIG_8xx
-#define NO_CONTEXT 16
-#define LAST_CONTEXT 15
-#define FIRST_CONTEXT 0
-
-#elif defined(CONFIG_4xx)
-#define NO_CONTEXT 256
-#define LAST_CONTEXT 255
-#define FIRST_CONTEXT 1
-
-#elif defined(CONFIG_E200) || defined(CONFIG_E500)
-#define NO_CONTEXT 256
-#define LAST_CONTEXT 255
-#define FIRST_CONTEXT 1
-
-#else
-
-/* PPC 6xx, 7xx CPUs */
-#define NO_CONTEXT ((unsigned long) -1)
-#define LAST_CONTEXT 32767
-#define FIRST_CONTEXT 1
-#endif
-
-/*
- * Set the current MMU context.
- * On 32-bit PowerPCs (other than the 8xx embedded chips), this is done by
- * loading up the segment registers for the user part of the address space.
- *
- * Since the PGD is immediately available, it is much faster to simply
- * pass this along as a second parameter, which is required for 8xx and
- * can be used for debugging on all processors (if you happen to have
- * an Abatron).
- */
-extern void set_context(unsigned long contextid, pgd_t *pgd);
-
-/*
- * Bitmap of contexts in use.
- * The size of this bitmap is LAST_CONTEXT + 1 bits.
- */
-extern unsigned long context_map[];
-
-/*
- * This caches the next context number that we expect to be free.
- * Its use is an optimization only, we can't rely on this context
- * number to be free, but it usually will be.
- */
-extern unsigned long next_mmu_context;
-
-/*
- * If we don't have sufficient contexts to give one to every task
- * that could be in the system, we need to be able to steal contexts.
- * These variables support that.
- */
-#if LAST_CONTEXT < 30000
-#define FEW_CONTEXTS 1
-extern atomic_t nr_free_contexts;
-extern struct mm_struct *context_mm[LAST_CONTEXT+1];
-extern void steal_context(void);
-#endif
-
-/*
- * Get a new mmu context for the address space described by `mm'.
- */
-static inline void get_mmu_context(struct mm_struct *mm)
-{
- unsigned long ctx;
-
- if (mm->context.id != NO_CONTEXT)
- return;
-#ifdef FEW_CONTEXTS
- while (atomic_dec_if_positive(&nr_free_contexts) < 0)
- steal_context();
-#endif
- 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;
- mm->context.id = ctx;
-#ifdef FEW_CONTEXTS
- context_mm[ctx] = mm;
-#endif
-}
-
-/*
- * Set up the context for a new address space.
- */
-static inline int init_new_context(struct task_struct *t, struct mm_struct *mm)
-{
- mm->context.id = NO_CONTEXT;
- return 0;
-}
-
-/*
- * We're finished using the context for an address space.
- */
-static inline void destroy_context(struct mm_struct *mm)
-{
- preempt_disable();
- if (mm->context.id != NO_CONTEXT) {
- clear_bit(mm->context.id, context_map);
- mm->context.id = NO_CONTEXT;
-#ifdef FEW_CONTEXTS
- atomic_inc(&nr_free_contexts);
-#endif
- }
- preempt_enable();
-}
-
-static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
- struct task_struct *tsk)
-{
-#ifdef CONFIG_ALTIVEC
- if (cpu_has_feature(CPU_FTR_ALTIVEC))
- asm volatile ("dssall;\n"
-#ifndef CONFIG_POWER4
- "sync;\n" /* G4 needs a sync here, G5 apparently not */
-#endif
- : : );
-#endif /* CONFIG_ALTIVEC */
-
- tsk->thread.pgdir = next->pgd;
-
- if (!cpu_isset(smp_processor_id(), next->cpu_vm_mask))
- cpu_set(smp_processor_id(), next->cpu_vm_mask);
-
- /* No need to flush userspace segments if the mm doesnt change */
- if (prev == next)
- return;
-
- /* Setup new userspace context */
- get_mmu_context(next);
- set_context(next->context.id, next->pgd);
-}
-
-#define deactivate_mm(tsk,mm) do { } while (0)
+#include <asm/cputhreads.h>
/*
- * After we have set current->mm to a new value, this activates
- * the context for the new mm so we see the new mappings.
+ * Most if the context management is out of line
*/
-#define activate_mm(active_mm, mm) switch_mm(active_mm, mm, current)
-
extern void mmu_context_init(void);
-
-
-#else
-
-#include <linux/kernel.h>
-#include <linux/mm.h>
-#include <linux/sched.h>
-
-/*
- * Copyright (C) 2001 PPC 64 Team, IBM Corp
- *
- * 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.
- */
-
-static inline void enter_lazy_tlb(struct mm_struct *mm,
- struct task_struct *tsk)
-{
-}
-
-/*
- * The proto-VSID space has 2^35 - 1 segments available for user mappings.
- * Each segment contains 2^28 bytes. Each context maps 2^44 bytes,
- * so we can support 2^19-1 contexts (19 == 35 + 28 - 44).
- */
-#define NO_CONTEXT 0
-#define MAX_CONTEXT ((1UL << 19) - 1)
-
extern int init_new_context(struct task_struct *tsk, struct mm_struct *mm);
extern void destroy_context(struct mm_struct *mm);
+extern void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next);
extern void switch_stab(struct task_struct *tsk, struct mm_struct *mm);
extern void switch_slb(struct task_struct *tsk, struct mm_struct *mm);
+extern void set_context(unsigned long id, pgd_t *pgd);
/*
* switch_mm is the entry point called from the architecture independent
@@ -244,22 +30,39 @@ extern void switch_slb(struct task_struc
static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
struct task_struct *tsk)
{
- if (!cpu_isset(smp_processor_id(), next->cpu_vm_mask))
- cpu_set(smp_processor_id(), next->cpu_vm_mask);
+ /* Mark this context has been used on the new CPU */
+ cpu_set(smp_processor_id(), next->cpu_vm_mask);
+
+ /* 32-bit keeps track of the current PGDIR in the thread struct */
+#ifdef CONFIG_PPC32
+ tsk->thread.pgdir = next->pgd;
+#endif /* CONFIG_PPC32 */
- /* No need to flush userspace segments if the mm doesnt change */
+ /* 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
+ */
#ifdef CONFIG_ALTIVEC
if (cpu_has_feature(CPU_FTR_ALTIVEC))
asm volatile ("dssall");
#endif /* CONFIG_ALTIVEC */
+ /* The actual HW switching method differs between the various
+ * sub architectures.
+ */
+#ifdef CONFIG_PPC_STD_MMU_64
if (cpu_has_feature(CPU_FTR_SLB))
switch_slb(tsk, next);
else
switch_stab(tsk, next);
+#else
+ /* Out of line for now */
+ switch_mmu_context(prev, next);
+#endif
+
}
#define deactivate_mm(tsk,mm) do { } while (0)
@@ -277,6 +80,11 @@ static inline void activate_mm(struct mm
local_irq_restore(flags);
}
-#endif /* CONFIG_PPC64 */
+/* We don't currently use enter_lazy_tlb() for anything */
+static inline void enter_lazy_tlb(struct mm_struct *mm,
+ struct task_struct *tsk)
+{
+}
+
#endif /* __KERNEL__ */
#endif /* __ASM_POWERPC_MMU_CONTEXT_H */
Index: linux-work/arch/powerpc/kernel/asm-offsets.c
===================================================================
--- linux-work.orig/arch/powerpc/kernel/asm-offsets.c 2008-12-08 14:37:13.000000000 +1100
+++ linux-work/arch/powerpc/kernel/asm-offsets.c 2008-12-08 14:45:47.000000000 +1100
@@ -60,6 +60,7 @@ int main(void)
{
DEFINE(THREAD, offsetof(struct task_struct, thread));
DEFINE(MM, offsetof(struct task_struct, mm));
+ DEFINE(MMCONTEXTID, offsetof(struct mm_struct, context.id));
#ifdef CONFIG_PPC64
DEFINE(AUDITCONTEXT, offsetof(struct task_struct, audit_context));
#else
Index: linux-work/arch/powerpc/kernel/head_32.S
===================================================================
--- linux-work.orig/arch/powerpc/kernel/head_32.S 2008-12-08 14:37:13.000000000 +1100
+++ linux-work/arch/powerpc/kernel/head_32.S 2008-12-08 14:47:03.000000000 +1100
@@ -31,6 +31,7 @@
#include <asm/ppc_asm.h>
#include <asm/asm-offsets.h>
#include <asm/ptrace.h>
+#include <asm/bug.h>
/* 601 only have IBAT; cr0.eq is set on 601 when using this macro */
#define LOAD_BAT(n, reg, RA, RB) \
@@ -1070,9 +1071,14 @@ start_here:
RFI
/*
+ * void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next);
+ *
* Set up the segment registers for a new context.
*/
-_ENTRY(set_context)
+_ENTRY(switch_mmu_context)
+ lwz r3,MMCONTEXTID(r4)
+ cmpwi cr0,r3,0
+ blt- 4f
mulli r3,r3,897 /* multiply context by skew factor */
rlwinm r3,r3,4,8,27 /* VSID = (context & 0xfffff) << 4 */
addis r3,r3,0x6000 /* Set Ks, Ku bits */
@@ -1083,6 +1089,7 @@ _ENTRY(set_context)
/* Context switch the PTE pointer for the Abatron BDI2000.
* The PGDIR is passed as second argument.
*/
+ lwz r4,MM_PGD(r4)
lis r5, KERNELBASE at h
lwz r5, 0xf0(r5)
stw r4, 0x4(r5)
@@ -1098,6 +1105,9 @@ _ENTRY(set_context)
sync
isync
blr
+4: trap
+ EMIT_BUG_ENTRY 4b,__FILE__,__LINE__,0
+ blr
/*
* An undocumented "feature" of 604e requires that the v bit
Index: linux-work/arch/powerpc/kernel/ppc_ksyms.c
===================================================================
--- linux-work.orig/arch/powerpc/kernel/ppc_ksyms.c 2008-12-08 14:37:13.000000000 +1100
+++ linux-work/arch/powerpc/kernel/ppc_ksyms.c 2008-12-08 14:45:47.000000000 +1100
@@ -174,8 +174,7 @@ EXPORT_SYMBOL(cacheable_memcpy);
#endif
#ifdef CONFIG_PPC32
-EXPORT_SYMBOL(next_mmu_context);
-EXPORT_SYMBOL(set_context);
+EXPORT_SYMBOL(switch_mmu_context);
#endif
#ifdef CONFIG_PPC_STD_MMU_32
Index: linux-work/arch/powerpc/kernel/swsusp.c
===================================================================
--- linux-work.orig/arch/powerpc/kernel/swsusp.c 2008-12-08 14:37:13.000000000 +1100
+++ linux-work/arch/powerpc/kernel/swsusp.c 2008-12-08 14:45:47.000000000 +1100
@@ -34,6 +34,6 @@ void save_processor_state(void)
void restore_processor_state(void)
{
#ifdef CONFIG_PPC32
- set_context(current->active_mm->context.id, current->active_mm->pgd);
+ switch_mmu_context(NULL, current->active_mm);
#endif
}
Index: linux-work/arch/powerpc/mm/Makefile
===================================================================
--- linux-work.orig/arch/powerpc/mm/Makefile 2008-12-08 14:37:13.000000000 +1100
+++ linux-work/arch/powerpc/mm/Makefile 2008-12-08 14:46:25.000000000 +1100
@@ -8,15 +8,16 @@ endif
obj-y := fault.o mem.o pgtable.o \
init_$(CONFIG_WORD_SIZE).o \
- pgtable_$(CONFIG_WORD_SIZE).o \
- mmu_context_$(CONFIG_WORD_SIZE).o
+ pgtable_$(CONFIG_WORD_SIZE).o
+obj-$(CONFIG_PPC_MMU_NOHASH) += mmu_context_nohash.o
hash-$(CONFIG_PPC_NATIVE) := hash_native_64.o
obj-$(CONFIG_PPC64) += hash_utils_64.o \
slb_low.o slb.o stab.o \
gup.o mmap.o $(hash-y)
obj-$(CONFIG_PPC_STD_MMU_32) += ppc_mmu_32.o
obj-$(CONFIG_PPC_STD_MMU) += hash_low_$(CONFIG_WORD_SIZE).o \
- tlb_$(CONFIG_WORD_SIZE).o
+ tlb_$(CONFIG_WORD_SIZE).o \
+ mmu_context_hash$(CONFIG_WORD_SIZE).o
obj-$(CONFIG_40x) += 40x_mmu.o
obj-$(CONFIG_44x) += 44x_mmu.o
obj-$(CONFIG_FSL_BOOKE) += fsl_booke_mmu.o
Index: linux-work/arch/powerpc/mm/mmu_context_hash32.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-work/arch/powerpc/mm/mmu_context_hash32.c 2008-12-08 14:45:47.000000000 +1100
@@ -0,0 +1,103 @@
+/*
+ * 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,
+ * 8260, and POWER3 implementations but excludes the 8xx and 4xx.
+ * -- paulus
+ *
+ * Derived from arch/ppc/mm/init.c:
+ * Copyright (C) 1995-1996 Gary Thomas (gdt at linuxppc.org)
+ *
+ * Modifications by Paul Mackerras (PowerMac) (paulus at cs.anu.edu.au)
+ * and Cort Dougan (PReP) (cort at 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 <asm/mmu_context.h>
+#include <asm/tlbflush.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];
+
+
+/*
+ * Set up the context for a new address space.
+ */
+int init_new_context(struct task_struct *t, struct mm_struct *mm)
+{
+ 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;
+ mm->context.id = ctx;
+
+ return 0;
+}
+
+/*
+ * 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) {
+ clear_bit(mm->context.id, context_map);
+ 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;
+}
Index: linux-work/arch/powerpc/mm/mmu_context_hash64.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-work/arch/powerpc/mm/mmu_context_hash64.c 2008-12-08 14:45:47.000000000 +1100
@@ -0,0 +1,78 @@
+/*
+ * MMU context allocation for 64-bit kernels.
+ *
+ * Copyright (C) 2004 Anton Blanchard, IBM Corp. <anton at samba.org>
+ *
+ * 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/sched.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/mm.h>
+#include <linux/spinlock.h>
+#include <linux/idr.h>
+
+#include <asm/mmu_context.h>
+
+static DEFINE_SPINLOCK(mmu_context_lock);
+static DEFINE_IDR(mmu_context_idr);
+
+/*
+ * The proto-VSID space has 2^35 - 1 segments available for user mappings.
+ * Each segment contains 2^28 bytes. Each context maps 2^44 bytes,
+ * so we can support 2^19-1 contexts (19 == 35 + 28 - 44).
+ */
+#define NO_CONTEXT 0
+#define MAX_CONTEXT ((1UL << 19) - 1)
+
+int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
+{
+ int index;
+ int err;
+
+again:
+ if (!idr_pre_get(&mmu_context_idr, GFP_KERNEL))
+ return -ENOMEM;
+
+ spin_lock(&mmu_context_lock);
+ err = idr_get_new_above(&mmu_context_idr, NULL, 1, &index);
+ spin_unlock(&mmu_context_lock);
+
+ if (err == -EAGAIN)
+ goto again;
+ else if (err)
+ return err;
+
+ if (index > MAX_CONTEXT) {
+ spin_lock(&mmu_context_lock);
+ idr_remove(&mmu_context_idr, index);
+ spin_unlock(&mmu_context_lock);
+ return -ENOMEM;
+ }
+
+ /* The old code would re-promote on fork, we don't do that
+ * when using slices as it could cause problem promoting slices
+ * that have been forced down to 4K
+ */
+ if (slice_mm_new_context(mm))
+ slice_set_user_psize(mm, mmu_virtual_psize);
+ mm->context.id = index;
+
+ return 0;
+}
+
+void destroy_context(struct mm_struct *mm)
+{
+ spin_lock(&mmu_context_lock);
+ idr_remove(&mmu_context_idr, mm->context.id);
+ spin_unlock(&mmu_context_lock);
+
+ mm->context.id = NO_CONTEXT;
+}
Index: linux-work/arch/powerpc/mm/mmu_context_nohash.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-work/arch/powerpc/mm/mmu_context_nohash.c 2008-12-08 14:46:34.000000000 +1100
@@ -0,0 +1,162 @@
+/*
+ * This file contains the routines for handling the MMU on those
+ * PowerPC implementations where the MMU is not using the hash
+ * table, such as 8xx, 4xx, BookE's etc...
+ *
+ * Copyright 2008 Ben Herrenschmidt <benh at kernel.crashing.org>
+ * IBM Corp.
+ *
+ * Derived from previous arch/powerpc/mm/mmu_context.c
+ * and arch/powerpc/include/asm/mmu_context.h
+ *
+ * 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 <asm/mmu_context.h>
+#include <asm/tlbflush.h>
+
+/*
+ * The MPC8xx has only 16 contexts. We rotate through them on each
+ * task switch. A better way would be to keep track of tasks that
+ * own contexts, and implement an LRU usage. That way very active
+ * tasks don't always have to pay the TLB reload overhead. The
+ * kernel pages are mapped shared, so the kernel can run on behalf
+ * of any task that makes a kernel entry. Shared does not mean they
+ * are not protected, just that the ASID comparison is not performed.
+ * -- Dan
+ *
+ * The IBM4xx has 256 contexts, so we can just rotate through these
+ * as a way of "switching" contexts. If the TID of the TLB is zero,
+ * the PID/TID comparison is disabled, so we can use a TID of zero
+ * to represent all kernel pages as shared among all contexts.
+ * -- Dan
+ */
+
+#ifdef CONFIG_8xx
+#define NO_CONTEXT 16
+#define LAST_CONTEXT 15
+#define FIRST_CONTEXT 0
+
+#elif defined(CONFIG_4xx)
+#define NO_CONTEXT 256
+#define LAST_CONTEXT 255
+#define FIRST_CONTEXT 1
+
+#elif defined(CONFIG_E200) || defined(CONFIG_E500)
+#define NO_CONTEXT 256
+#define LAST_CONTEXT 255
+#define FIRST_CONTEXT 1
+
+#else
+#error Unsupported processor type
+#endif
+
+static unsigned long next_mmu_context;
+static unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1];
+static atomic_t nr_free_contexts;
+static struct mm_struct *context_mm[LAST_CONTEXT+1];
+static void steal_context(void);
+
+/* Steal a context from a task that has one at the moment.
+ * This is only used on 8xx and 4xx and we presently assume that
+ * they don't do SMP. If they do then this will have to check
+ * whether the MM we steal is in use.
+ * We also assume that this is only used on systems that don't
+ * use an MMU hash table - this is true for 8xx and 4xx.
+ * This isn't an LRU system, it just frees up each context in
+ * turn (sort-of pseudo-random replacement :). This would be the
+ * place to implement an LRU scheme if anyone was motivated to do it.
+ * -- paulus
+ */
+static void steal_context(void)
+{
+ struct mm_struct *mm;
+
+ /* free up context `next_mmu_context' */
+ /* if we shouldn't free context 0, don't... */
+ if (next_mmu_context < FIRST_CONTEXT)
+ next_mmu_context = FIRST_CONTEXT;
+ mm = context_mm[next_mmu_context];
+ flush_tlb_mm(mm);
+ destroy_context(mm);
+}
+
+
+/*
+ * Get a new mmu context for the address space described by `mm'.
+ */
+static inline void get_mmu_context(struct mm_struct *mm)
+{
+ unsigned long ctx;
+
+ if (mm->context.id != NO_CONTEXT)
+ return;
+
+ while (atomic_dec_if_positive(&nr_free_contexts) < 0)
+ steal_context();
+
+ 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;
+ mm->context.id = ctx;
+ context_mm[ctx] = mm;
+}
+
+void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next)
+{
+ get_mmu_context(next);
+
+ set_context(next->context.id, next->pgd);
+}
+
+/*
+ * Set up the context for a new address space.
+ */
+int init_new_context(struct task_struct *t, struct mm_struct *mm)
+{
+ mm->context.id = NO_CONTEXT;
+ return 0;
+}
+
+/*
+ * 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) {
+ clear_bit(mm->context.id, context_map);
+ mm->context.id = NO_CONTEXT;
+ atomic_inc(&nr_free_contexts);
+ }
+ preempt_enable();
+}
+
+
+/*
+ * Initialize the context management stuff.
+ */
+void __init mmu_context_init(void)
+{
+ /*
+ * Some processors have too few contexts to reserve one for
+ * init_mm, and require using context 0 for a normal task.
+ * Other processors reserve the use of context zero for the kernel.
+ * This code assumes FIRST_CONTEXT < 32.
+ */
+ context_map[0] = (1 << FIRST_CONTEXT) - 1;
+ next_mmu_context = FIRST_CONTEXT;
+ atomic_set(&nr_free_contexts, LAST_CONTEXT - FIRST_CONTEXT + 1);
+}
+
Index: linux-work/arch/powerpc/platforms/Kconfig.cputype
===================================================================
--- linux-work.orig/arch/powerpc/platforms/Kconfig.cputype 2008-12-08 14:37:13.000000000 +1100
+++ linux-work/arch/powerpc/platforms/Kconfig.cputype 2008-12-08 14:45:47.000000000 +1100
@@ -195,13 +195,21 @@ config SPE
config PPC_STD_MMU
bool
- depends on 6xx || POWER3 || POWER4 || PPC64
+ depends on 6xx || PPC64
default y
config PPC_STD_MMU_32
def_bool y
depends on PPC_STD_MMU && PPC32
+config PPC_STD_MMU_64
+ def_bool y
+ depends on PPC_STD_MMU && PPC64
+
+config PPC_MMU_NOHASH
+ def_bool y
+ depends on !PPC_STD_MMU
+
config PPC_MM_SLICES
bool
default y if HUGETLB_PAGE || PPC_64K_PAGES
Index: linux-work/arch/powerpc/platforms/powermac/cpufreq_32.c
===================================================================
--- linux-work.orig/arch/powerpc/platforms/powermac/cpufreq_32.c 2008-12-08 14:37:13.000000000 +1100
+++ linux-work/arch/powerpc/platforms/powermac/cpufreq_32.c 2008-12-08 14:45:47.000000000 +1100
@@ -310,7 +310,7 @@ static int pmu_set_cpu_speed(int low_spe
_set_L3CR(save_l3cr);
/* Restore userland MMU context */
- set_context(current->active_mm->context.id, current->active_mm->pgd);
+ switch_mmu_context(NULL, current->active_mm);
#ifdef DEBUG_FREQ
printk(KERN_DEBUG "HID1, after: %x\n", mfspr(SPRN_HID1));
Index: linux-work/drivers/macintosh/via-pmu.c
===================================================================
--- linux-work.orig/drivers/macintosh/via-pmu.c 2008-12-08 14:37:13.000000000 +1100
+++ linux-work/drivers/macintosh/via-pmu.c 2008-12-08 14:45:47.000000000 +1100
@@ -1814,7 +1814,7 @@ static int powerbook_sleep_grackle(void)
_set_L2CR(save_l2cr);
/* Restore userland MMU context */
- set_context(current->active_mm->context.id, current->active_mm->pgd);
+ switch_mmu_context(NULL, current->active_mm);
/* Power things up */
pmu_unlock();
@@ -1903,7 +1903,7 @@ powerbook_sleep_Core99(void)
_set_L3CR(save_l3cr);
/* Restore userland MMU context */
- set_context(current->active_mm->context.id, current->active_mm->pgd);
+ switch_mmu_context(NULL, current->active_mm);
/* Tell PMU we are ready */
pmu_unlock();
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