microblaze_mmu_v2: Context handling - mmu_context.c/h

/*

 * Copyright (C) 2006 Atmark Techno, Inc.

 *

 * This file is subject to the terms and conditions of the GNU General Public

 * License. See the file "COPYING" in the main directory of this archive

 * for more details.

 */

#ifndef _ASM_MICROBLAZE_MMU_CONTEXT_H

#define _ASM_MICROBLAZE_MMU_CONTEXT_H

# define init_new_context(tsk, mm)		({ 0; })

# define enter_lazy_tlb(mm, tsk)		do {} while (0)

# define change_mm_context(old, ctx, _pml4)	do {} while (0)

# define destroy_context(mm)			do {} while (0)

# define deactivate_mm(tsk, mm)			do {} while (0)

# define switch_mm(prev, next, tsk)		do {} while (0)

# define activate_mm(prev, next)		do {} while (0)

#endif /* _ASM_MICROBLAZE_MMU_CONTEXT_H */

#ifdef CONFIG_MMU

# include "mmu_context_mm.h"

#else

# include "mmu_context_no.h"

#endif

/*

 * Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>

 * Copyright (C) 2008-2009 PetaLogix

 * Copyright (C) 2006 Atmark Techno, Inc.

 *

 * This file is subject to the terms and conditions of the GNU General Public

 * License. See the file "COPYING" in the main directory of this archive

 * for more details.

 */

#ifndef _ASM_MICROBLAZE_MMU_CONTEXT_H

#define _ASM_MICROBLAZE_MMU_CONTEXT_H

#include <asm/atomic.h>

#include <asm/bitops.h>

#include <asm/mmu.h>

#include <asm-generic/mm_hooks.h>

# ifdef __KERNEL__

/*

 * 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.

 */

# define CTX_TO_VSID(ctx, va)	(((ctx) * (897 * 16) + ((va) >> 28) * 0x111) \

				 & 0xffffff)

/*

   MicroBlaze 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.

 */

static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)

{

}

# define NO_CONTEXT	256

# define LAST_CONTEXT	255

# define FIRST_CONTEXT	1

/*

 * Set the current MMU context.

 * This is done byloading 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(mm_context_t context, 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 mm_context_t next_mmu_context;

/*

 * Since 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.

 */

extern atomic_t nr_free_contexts;

extern struct mm_struct *context_mm[LAST_CONTEXT+1];

extern void steal_context(void);

/*

 * Get a new mmu context for the address space described by `mm'.

 */

static inline void get_mmu_context(struct mm_struct *mm)

{

	mm_context_t ctx;

	if (mm->context != 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 = ctx;

	context_mm[ctx] = mm;

}

/*

 * Set up the context for a new address space.

 */

# define init_new_context(tsk, mm)	(((mm)->context = NO_CONTEXT), 0)

/*

 * We're finished using the context for an address space.

 */

static inline void destroy_context(struct mm_struct *mm)

{

	if (mm->context != NO_CONTEXT) {

		clear_bit(mm->context, context_map);

		mm->context = NO_CONTEXT;

		atomic_inc(&nr_free_contexts);

	}

}

static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,

			     struct task_struct *tsk)

{

	tsk->thread.pgdir = next->pgd;

	get_mmu_context(next);

	set_context(next->context, next->pgd);

}

/*

 * After we have set current->mm to a new value, this activates

 * the context for the new mm so we see the new mappings.

 */

static inline void activate_mm(struct mm_struct *active_mm,

			struct mm_struct *mm)

{

	current->thread.pgdir = mm->pgd;

	get_mmu_context(mm);

	set_context(mm->context, mm->pgd);

}

extern void mmu_context_init(void);

# endif /* __KERNEL__ */

#endif /* _ASM_MICROBLAZE_MMU_CONTEXT_H */

/*

 * Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>

 * Copyright (C) 2008-2009 PetaLogix

 * Copyright (C) 2006 Atmark Techno, Inc.

 *

 * This file is subject to the terms and conditions of the GNU General Public

 * License. See the file "COPYING" in the main directory of this archive

 * for more details.

 */

#ifndef _ASM_MICROBLAZE_MMU_CONTEXT_H

#define _ASM_MICROBLAZE_MMU_CONTEXT_H

# define init_new_context(tsk, mm)		({ 0; })

# define enter_lazy_tlb(mm, tsk)		do {} while (0)

# define change_mm_context(old, ctx, _pml4)	do {} while (0)

# define destroy_context(mm)			do {} while (0)

# define deactivate_mm(tsk, mm)			do {} while (0)

# define switch_mm(prev, next, tsk)		do {} while (0)

# define activate_mm(prev, next)		do {} while (0)

#endif /* _ASM_MICROBLAZE_MMU_CONTEXT_H */

/*

 * This file contains the routines for handling the MMU.

 *

 *    Copyright (C) 2007 Xilinx, Inc.  All rights reserved.

 *

 *  Derived from arch/ppc/mm/4xx_mmu.c:

 *  -- 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

 *  Amiga/APUS changes by Jesper Skov (jskov@cygnus.co.uk).

 *

 *  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/tlbflush.h>

#include <asm/mmu_context.h>

mm_context_t next_mmu_context;

unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1];

atomic_t nr_free_contexts;

struct mm_struct *context_mm[LAST_CONTEXT+1];

/*

 * Initialize the context management stuff.

 */

void __init mmu_context_init(void)

{

	/*

	 * The use of context zero is reserved 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);

}

/*

 * Steal a context from a task that has one at the moment.

 *

 * 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 were motivated to do it.

 */

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);

}