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/*
* 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 <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;
}
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