2 * linux/arch/cris/mm/tlb.c
4 * Copyright (C) 2000, 2001 Axis Communications AB
6 * Authors: Bjorn Wesen (bjornw@axis.com)
10 #include <linux/init.h>
11 #include <linux/kernel.h>
12 #include <linux/mm_types.h>
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
21 * of which mm we have assigned to which page_id, so that we know when
22 * to invalidate TLB entries.
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.
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
32 struct mm_struct *page_id_map[NUM_PAGEID];
33 static int map_replace_ptr = 1; /* which page_id_map entry to replace next */
35 /* the following functions are similar to those used in the PPC port */
38 alloc_context(struct mm_struct *mm)
40 struct mm_struct *old_mm;
42 D(printk("tlb: alloc context %d (%p)\n", map_replace_ptr, mm));
44 /* did we replace an mm ? */
46 old_mm = page_id_map[map_replace_ptr];
49 /* throw out any TLB entries belonging to the mm we replace
54 old_mm->context.page_id = NO_CONTEXT;
57 /* insert it into the page_id_map */
59 mm->context.page_id = map_replace_ptr;
60 page_id_map[map_replace_ptr] = mm;
64 if(map_replace_ptr == INVALID_PAGEID)
65 map_replace_ptr = 0; /* wrap around */
69 * if needed, get a new MMU context for the mm. otherwise nothing is done.
73 get_mmu_context(struct mm_struct *mm)
75 if(mm->context.page_id == NO_CONTEXT)
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
83 * the only thing we really need to do here is mark the used PID slot
88 destroy_context(struct mm_struct *mm)
90 if(mm->context.page_id != NO_CONTEXT) {
91 D(printk("destroy_context %d (%p)\n", mm->context.page_id, mm));
92 flush_tlb_mm(mm); /* TODO this might be redundant ? */
93 page_id_map[mm->context.page_id] = NULL;
97 /* called once during VM initialization, from init.c */
104 /* clear the page_id map */
106 for (i = 1; i < ARRAY_SIZE(page_id_map); i++)
107 page_id_map[i] = NULL;
109 /* invalidate the entire TLB */
113 /* the init_mm has context 0 from the boot */
115 page_id_map[0] = &init_mm;