[linux-2.6-block.git] / arch / cris / mm / tlb.c

/*
 *  linux/arch/cris/mm/tlb.c
 *
 *  Copyright (C) 2000, 2001  Axis Communications AB
 *  
 *  Authors:   Bjorn Wesen (bjornw@axis.com)
 *
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm_types.h>

#include <asm/tlb.h>

#define D(x)

/* The TLB can host up to 64 different mm contexts at the same time.
 * The running context is R_MMU_CONTEXT, and each TLB entry contains a
 * page_id that has to match to give a hit. In page_id_map, we keep track
 * of which mm we have assigned to which page_id, so that we know when
 * to invalidate TLB entries.
 *
 * The last page_id is never running - it is used as an invalid page_id
 * so we can make TLB entries that will never match.
 *
 * Notice that we need to make the flushes atomic, otherwise an interrupt
 * handler that uses vmalloced memory might cause a TLB load in the middle
 * of a flush causing.
 */

struct mm_struct *page_id_map[NUM_PAGEID];
static int map_replace_ptr = 1;  /* which page_id_map entry to replace next */

/* the following functions are similar to those used in the PPC port */

static inline void
alloc_context(struct mm_struct *mm)
{
	struct mm_struct *old_mm;

	D(printk("tlb: alloc context %d (%p)\n", map_replace_ptr, mm));

	/* did we replace an mm ? */

	old_mm = page_id_map[map_replace_ptr];

	if(old_mm) {
		/* throw out any TLB entries belonging to the mm we replace
		 * in the map
		 */
		flush_tlb_mm(old_mm);

		old_mm->context.page_id = NO_CONTEXT;
	}

	/* insert it into the page_id_map */

	mm->context.page_id = map_replace_ptr;
	page_id_map[map_replace_ptr] = mm;

	map_replace_ptr++;

	if(map_replace_ptr == INVALID_PAGEID)
		map_replace_ptr = 0;         /* wrap around */	
}

/* 
 * if needed, get a new MMU context for the mm. otherwise nothing is done.
 */

void
get_mmu_context(struct mm_struct *mm)
{
	if(mm->context.page_id == NO_CONTEXT)
		alloc_context(mm);
}

/* called by __exit_mm to destroy the used MMU context if any before
 * destroying the mm itself. this is only called when the last user of the mm
 * drops it.
 *
 * the only thing we really need to do here is mark the used PID slot
 * as empty.
 */

void
destroy_context(struct mm_struct *mm)
{
	if(mm->context.page_id != NO_CONTEXT) {
		D(printk("destroy_context %d (%p)\n", mm->context.page_id, mm));
		flush_tlb_mm(mm);  /* TODO this might be redundant ? */
		page_id_map[mm->context.page_id] = NULL;
	}
}

/* called once during VM initialization, from init.c */

void __init
tlb_init(void)
{
	int i;

	/* clear the page_id map */

	for (i = 1; i < ARRAY_SIZE(page_id_map); i++)
		page_id_map[i] = NULL;
	
	/* invalidate the entire TLB */

	flush_tlb_all();

	/* the init_mm has context 0 from the boot */

	page_id_map[0] = &init_mm;
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/arch/cris/mm/tlb.c
	3	*
	4	* Copyright (C) 2000, 2001 Axis Communications AB
	5	*
	6	* Authors: Bjorn Wesen (bjornw@axis.com)
	7	*
	8	*/
	9
	10	#include <linux/init.h>
8447157a	11	#include <linux/kernel.h>
589ee628 IM	12	#include <linux/mm_types.h>
589ee628 IM	13
1da177e4 LT	14	#include <asm/tlb.h>
	15
	16	#define D(x)
	17
	18	/* The TLB can host up to 64 different mm contexts at the same time.
	19	* The running context is R_MMU_CONTEXT, and each TLB entry contains a
	20	* page_id that has to match to give a hit. In page_id_map, we keep track
49b4ff33	21	* of which mm we have assigned to which page_id, so that we know when
1da177e4 LT	22	* to invalidate TLB entries.
	23	*
	24	* The last page_id is never running - it is used as an invalid page_id
	25	* so we can make TLB entries that will never match.
	26	*
	27	* Notice that we need to make the flushes atomic, otherwise an interrupt
	28	* handler that uses vmalloced memory might cause a TLB load in the middle
	29	* of a flush causing.
	30	*/
	31
	32	struct mm_struct *page_id_map[NUM_PAGEID];
	33	static int map_replace_ptr = 1; /* which page_id_map entry to replace next */
	34
1da177e4 LT	35	/* the following functions are similar to those used in the PPC port */
	36
	37	static inline void
	38	alloc_context(struct mm_struct *mm)
	39	{
	40	struct mm_struct *old_mm;
	41
	42	D(printk("tlb: alloc context %d (%p)\n", map_replace_ptr, mm));
	43
	44	/* did we replace an mm ? */
	45
	46	old_mm = page_id_map[map_replace_ptr];
	47
	48	if(old_mm) {
	49	/* throw out any TLB entries belonging to the mm we replace
	50	* in the map
	51	*/
	52	flush_tlb_mm(old_mm);
	53
4f18cfbf	54	old_mm->context.page_id = NO_CONTEXT;
1da177e4 LT	55	}
	56
	57	/* insert it into the page_id_map */
	58
4f18cfbf	59	mm->context.page_id = map_replace_ptr;
1da177e4 LT	60	page_id_map[map_replace_ptr] = mm;
	61
	62	map_replace_ptr++;
	63
	64	if(map_replace_ptr == INVALID_PAGEID)
	65	map_replace_ptr = 0; /* wrap around */
	66	}
	67
	68	/*
	69	* if needed, get a new MMU context for the mm. otherwise nothing is done.
	70	*/
	71
	72	void
	73	get_mmu_context(struct mm_struct *mm)
	74	{
4f18cfbf	75	if(mm->context.page_id == NO_CONTEXT)
1da177e4 LT	76	alloc_context(mm);
	77	}
	78
	79	/* called by __exit_mm to destroy the used MMU context if any before
	80	* destroying the mm itself. this is only called when the last user of the mm
	81	* drops it.
	82	*
	83	* the only thing we really need to do here is mark the used PID slot
	84	* as empty.
	85	*/
	86
	87	void
	88	destroy_context(struct mm_struct *mm)
	89	{
4f18cfbf MS	90	if(mm->context.page_id != NO_CONTEXT) {
4f18cfbf MS	91	D(printk("destroy_context %d (%p)\n", mm->context.page_id, mm));
1da177e4	92	flush_tlb_mm(mm); /* TODO this might be redundant ? */
4f18cfbf	93	page_id_map[mm->context.page_id] = NULL;
1da177e4 LT	94	}
	95	}
	96
	97	/* called once during VM initialization, from init.c */
	98
	99	void __init
	100	tlb_init(void)
	101	{
	102	int i;
	103
	104	/* clear the page_id map */
	105
8447157a	106	for (i = 1; i < ARRAY_SIZE(page_id_map); i++)
1da177e4 LT	107	page_id_map[i] = NULL;
	108
	109	/* invalidate the entire TLB */
	110
	111	flush_tlb_all();
	112
	113	/* the init_mm has context 0 from the boot */
	114
	115	page_id_map[0] = &init_mm;
	116	}