115 lines
2.6 KiB
C
115 lines
2.6 KiB
C
/*
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* linux/arch/cris/mm/tlb.c
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*
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* Copyright (C) 2000, 2001 Axis Communications AB
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*
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* Authors: Bjorn Wesen (bjornw@axis.com)
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*
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*/
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <asm/tlb.h>
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#define D(x)
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/* The TLB can host up to 64 different mm contexts at the same time.
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* The running context is R_MMU_CONTEXT, and each TLB entry contains a
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* page_id that has to match to give a hit. In page_id_map, we keep track
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* of which mm's we have assigned which page_id's, so that we know when
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* to invalidate TLB entries.
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*
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* The last page_id is never running - it is used as an invalid page_id
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* so we can make TLB entries that will never match.
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*
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* Notice that we need to make the flushes atomic, otherwise an interrupt
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* handler that uses vmalloced memory might cause a TLB load in the middle
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* of a flush causing.
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*/
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struct mm_struct *page_id_map[NUM_PAGEID];
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static int map_replace_ptr = 1; /* which page_id_map entry to replace next */
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/* the following functions are similar to those used in the PPC port */
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static inline void
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alloc_context(struct mm_struct *mm)
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{
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struct mm_struct *old_mm;
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D(printk("tlb: alloc context %d (%p)\n", map_replace_ptr, mm));
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/* did we replace an mm ? */
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old_mm = page_id_map[map_replace_ptr];
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if(old_mm) {
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/* throw out any TLB entries belonging to the mm we replace
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* in the map
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*/
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flush_tlb_mm(old_mm);
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old_mm->context.page_id = NO_CONTEXT;
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}
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/* insert it into the page_id_map */
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mm->context.page_id = map_replace_ptr;
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page_id_map[map_replace_ptr] = mm;
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map_replace_ptr++;
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if(map_replace_ptr == INVALID_PAGEID)
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map_replace_ptr = 0; /* wrap around */
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}
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/*
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* if needed, get a new MMU context for the mm. otherwise nothing is done.
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*/
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void
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get_mmu_context(struct mm_struct *mm)
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{
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if(mm->context.page_id == NO_CONTEXT)
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alloc_context(mm);
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}
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/* called by __exit_mm to destroy the used MMU context if any before
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* destroying the mm itself. this is only called when the last user of the mm
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* drops it.
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*
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* the only thing we really need to do here is mark the used PID slot
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* as empty.
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*/
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void
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destroy_context(struct mm_struct *mm)
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{
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if(mm->context.page_id != NO_CONTEXT) {
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D(printk("destroy_context %d (%p)\n", mm->context.page_id, mm));
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flush_tlb_mm(mm); /* TODO this might be redundant ? */
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page_id_map[mm->context.page_id] = NULL;
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}
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}
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/* called once during VM initialization, from init.c */
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void __init
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tlb_init(void)
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{
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int i;
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/* clear the page_id map */
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for (i = 1; i < ARRAY_SIZE(page_id_map); i++)
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page_id_map[i] = NULL;
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/* invalidate the entire TLB */
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flush_tlb_all();
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/* the init_mm has context 0 from the boot */
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page_id_map[0] = &init_mm;
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}
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