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740 jermar 1 
/*
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 * Copyright (C) 2006 Jakub Jermar
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 *
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 * - Redistributions of source code must retain the above copyright
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 *   notice, this list of conditions and the following disclaimer.
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 * - Redistributions in binary form must reproduce the above copyright
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 *   notice, this list of conditions and the following disclaimer in the
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 *   documentation and/or other materials provided with the distribution.
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 * - The name of the author may not be used to endorse or promote products
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 *   derived from this software without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */
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/*
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 * ASID management.
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 *
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 * Because ia64 has much wider ASIDs (18-24 bits) compared to other
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 * architectures (e.g. 8 bits on mips32 and 13 bits on sparc64), it is
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 * inappropriate to use same methods (i.e. genarch/mm/asid_fifo.c) for
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 * all of them.
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 *
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 * Instead, ia64 assigns ASID values from a counter that eventually
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 * overflows. When this happens, the counter is reset and all TLBs are
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 * entirely invalidated. Furthermore, all address space structures,
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 * except for the one with asid == ASID_KERNEL, are assigned new ASID.
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 *
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 * It is important to understand that, in SPARTAN, one ASID represents
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 * RIDS_PER_ASID consecutive hardware RIDs (Region ID's).
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 *
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 * Note that the algorithm used can handle only the maximum of
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 * ASID_OVERFLOW-ASID_START address spaces at a time.
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 */
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#include <arch/mm/asid.h>
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#include <mm/asid.h>
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#include <mm/as.h>
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#include <mm/tlb.h>
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#include <list.h>
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#include <typedefs.h>
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#include <debug.h>
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/**
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 * Stores the ASID to be returned next.
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 * Must be only accessed when asidlock is held.
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 */
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static asid_t next_asid = ASID_START;
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/** Assign next ASID.
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 *
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 * On ia64, this function is used only to allocate ASID
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 * for a newly created address space. As a side effect,
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 * it might attempt to shootdown TLBs and reassign
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 * ASIDs to existing address spaces.
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 *
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 * When calling this function, interrupts must be disabled
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 * and the asidlock must be held.
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 *
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 * @return ASID for new address space.
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 */
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asid_t asid_find_free(void)
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{
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    as_t *as;
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    link_t *cur;
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    if (next_asid == ASID_OVERFLOW) {
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        /*
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         * The counter has overflown.
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         */
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        /*
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         * Reset the counter.
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         */
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        next_asid = ASID_START;
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        /*
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         * Initiate TLB shootdown.
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         */
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        tlb_shootdown_start(TLB_INVL_ALL, 0, 0, 0);
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        /*
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         * Reassign ASIDs to existing address spaces.
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         */
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        for (cur = as_with_asid_head.next; cur != &as_with_asid_head; cur = cur->next) {
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            ASSERT(next_asid < ASID_OVERFLOW);
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            as = list_get_instance(cur, as_t, as_with_asid_link);
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            spinlock_lock(&as->lock);
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            as->asid = next_asid++;
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            spinlock_unlock(&as->lock);
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        }
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        /*
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         * Finish TLB shootdown.
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         */
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        tlb_shootdown_finalize();
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        tlb_invalidate_all();
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    }
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    ASSERT(next_asid < ASID_OVERFLOW);
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    return next_asid++;
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}