tlb.c

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/*
 *  linux/arch/cris/arch-v10/mm/tlb.c
 *
 *  Low level TLB handling
 *
 *
 *  Copyright (C) 2000-2007  Axis Communications AB
 *
 *  Authors:   Bjorn Wesen ([email protected])
 *
 */

#include <asm/tlb.h>
#include <asm/mmu_context.h>
#include <arch/svinto.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's we have assigned which page_id's, 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.
 */

/* invalidate all TLB entries */

void
flush_tlb_all(void)
{
    int i;
    unsigned long flags;

    /* the vpn of i & 0xf is so we dont write similar TLB entries
     * in the same 4-way entry group. details...
     */

    local_irq_save(flags);
    for(i = 0; i < NUM_TLB_ENTRIES; i++) {
        *R_TLB_SELECT = ( IO_FIELD(R_TLB_SELECT, index, i) );
        *R_TLB_HI = ( IO_FIELD(R_TLB_HI, page_id, INVALID_PAGEID ) |
                  IO_FIELD(R_TLB_HI, vpn,     i & 0xf ) );

        *R_TLB_LO = ( IO_STATE(R_TLB_LO, global,no       ) |
                  IO_STATE(R_TLB_LO, valid, no       ) |
                  IO_STATE(R_TLB_LO, kernel,no   ) |
                  IO_STATE(R_TLB_LO, we,    no       ) |
                  IO_FIELD(R_TLB_LO, pfn,   0        ) );
    }
    local_irq_restore(flags);
    D(printk("tlb: flushed all\n"));
}

/* invalidate the selected mm context only */

void
flush_tlb_mm(struct mm_struct *mm)
{
    int i;
    int page_id = mm->context.page_id;
    unsigned long flags;

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

    if(page_id == NO_CONTEXT)
        return;

    /* mark the TLB entries that match the page_id as invalid.
     * here we could also check the _PAGE_GLOBAL bit and NOT flush
     * global pages. is it worth the extra I/O ?
     */

    local_irq_save(flags);
    for(i = 0; i < NUM_TLB_ENTRIES; i++) {
        *R_TLB_SELECT = IO_FIELD(R_TLB_SELECT, index, i);
        if (IO_EXTRACT(R_TLB_HI, page_id, *R_TLB_HI) == page_id) {
            *R_TLB_HI = ( IO_FIELD(R_TLB_HI, page_id, INVALID_PAGEID ) |
                      IO_FIELD(R_TLB_HI, vpn,     i & 0xf ) );

            *R_TLB_LO = ( IO_STATE(R_TLB_LO, global,no  ) |
                      IO_STATE(R_TLB_LO, valid, no  ) |
                      IO_STATE(R_TLB_LO, kernel,no  ) |
                      IO_STATE(R_TLB_LO, we,    no  ) |
                      IO_FIELD(R_TLB_LO, pfn,   0   ) );
        }
    }
    local_irq_restore(flags);
}

/* invalidate a single page */

void flush_tlb_page(struct vm_area_struct *vma, unsigned long addr)
{
    struct mm_struct *mm = vma->vm_mm;
    int page_id = mm->context.page_id;
    int i;
    unsigned long flags;

    D(printk("tlb: flush page %p in context %d (%p)\n", addr, page_id, mm));

    if(page_id == NO_CONTEXT)
        return;

    addr &= PAGE_MASK; /* perhaps not necessary */

    /* invalidate those TLB entries that match both the mm context
     * and the virtual address requested
     */

    local_irq_save(flags);
    for(i = 0; i < NUM_TLB_ENTRIES; i++) {
        unsigned long tlb_hi;
        *R_TLB_SELECT = IO_FIELD(R_TLB_SELECT, index, i);
        tlb_hi = *R_TLB_HI;
        if (IO_EXTRACT(R_TLB_HI, page_id, tlb_hi) == page_id &&
            (tlb_hi & PAGE_MASK) == addr) {
            *R_TLB_HI = IO_FIELD(R_TLB_HI, page_id, INVALID_PAGEID ) |
                addr; /* same addr as before works. */

            *R_TLB_LO = ( IO_STATE(R_TLB_LO, global,no  ) |
                      IO_STATE(R_TLB_LO, valid, no  ) |
                      IO_STATE(R_TLB_LO, kernel,no  ) |
                      IO_STATE(R_TLB_LO, we,    no  ) |
                      IO_FIELD(R_TLB_LO, pfn,   0   ) );
        }
    }
    local_irq_restore(flags);
}

/*
 * Initialize the context related info for a new mm_struct
 * instance.
 */

int
init_new_context(struct task_struct *tsk, struct mm_struct *mm)
{
    mm->context.page_id = NO_CONTEXT;
    return 0;
}

/* called in schedule() just before actually doing the switch_to */

void switch_mm(struct mm_struct *prev, struct mm_struct *next,
    struct task_struct *tsk)
{
    if (prev != next) {
        /* make sure we have a context */
        get_mmu_context(next);

        /* remember the pgd for the fault handlers
         * this is similar to the pgd register in some other CPU's.
         * we need our own copy of it because current and active_mm
         * might be invalid at points where we still need to derefer
         * the pgd.
         */

        per_cpu(current_pgd, smp_processor_id()) = next->pgd;

        /* switch context in the MMU */

        D(printk(KERN_DEBUG "switching mmu_context to %d (%p)\n",
            next->context, next));

        *R_MMU_CONTEXT = IO_FIELD(R_MMU_CONTEXT,
                      page_id, next->context.page_id);
    }
}