powerpc/mm: Split mmu_context handling

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@kernel.crashing.org>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 34 insertions, 226 deletions

diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index b570209b71a..ab4f19263c4 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -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
-}
+#include <asm/cputhreads.h>
 
 /*
- * Set up the context for a new address space.
+ * Most if the context management is out of line
  */
-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)
-
-/*
- * After we have set current->mm to a new value, this activates
- * the context for the new mm so we see the new mappings.
- */
-#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_struct *tsk, struct mm_struct *mm);
 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_struct *prev, struct mm_struct *next)
 	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 */