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  1. /*
  2.  * Copyright (C) 2006 Jakub Jermar
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /*
  30.  * ASID management.
  31.  *
  32.  * Modern processor architectures optimize TLB utilization
  33.  * by using ASIDs (a.k.a. memory contexts on sparc64 and
  34.  * region identifiers on ia64). These ASIDs help to associate
  35.  * each TLB item with an address space, thus making
  36.  * finer-grained TLB invalidation possible.
  37.  *
  38.  * Unfortunatelly, there are usually less ASIDs available than
  39.  * there can be unique as_t structures (i.e. address spaces
  40.  * recognized by the kernel).
  41.  *
  42.  * When system runs short of ASIDs, it will attempt to steal
  43.  * ASID from an address space that has not been active for
  44.  * a while.
  45.  *
  46.  * This code depends on the fact that ASIDS_ALLOCABLE
  47.  * is greater than number of supported CPUs (i.e. the
  48.  * amount of concurently active address spaces).
  49.  *
  50.  * Architectures that don't have hardware support for address
  51.  * spaces do not compile with this file.
  52.  */
  53.  
  54. #include <mm/asid.h>
  55. #include <mm/as.h>
  56. #include <mm/tlb.h>
  57. #include <arch/mm/asid.h>
  58. #include <synch/spinlock.h>
  59. #include <arch.h>
  60. #include <adt/list.h>
  61. #include <debug.h>
  62.  
  63. /**
  64.  * asidlock protects the asids_allocated counter.
  65.  */
  66. SPINLOCK_INITIALIZE(asidlock);
  67.  
  68. static count_t asids_allocated = 0;
  69.  
  70. /** Allocate free address space identifier.
  71.  *
  72.  * Interrupts must be disabled and as_lock must be held
  73.  * prior to this call
  74.  *
  75.  * @return New ASID.
  76.  */
  77. asid_t asid_get(void)
  78. {
  79.     asid_t asid;
  80.     link_t *tmp;
  81.     as_t *as;
  82.  
  83.     /*
  84.      * Check if there is an unallocated ASID.
  85.      */
  86.    
  87.     spinlock_lock(&asidlock);
  88.     if (asids_allocated == ASIDS_ALLOCABLE) {
  89.  
  90.         /*
  91.          * All ASIDs are already allocated.
  92.          * Resort to stealing.
  93.          */
  94.        
  95.         /*
  96.          * Remove the first item on the list.
  97.          * It is guaranteed to belong to an
  98.          * inactive address space.
  99.          */
  100.         ASSERT(!list_empty(&inactive_as_with_asid_head));
  101.         tmp = inactive_as_with_asid_head.next;
  102.         list_remove(tmp);
  103.        
  104.         as = list_get_instance(tmp, as_t, inactive_as_with_asid_link);
  105.         spinlock_lock(&as->lock);
  106.  
  107.         /*
  108.          * Steal the ASID.
  109.          * Note that the stolen ASID is not active.
  110.          */
  111.         asid = as->asid;
  112.         ASSERT(asid != ASID_INVALID);
  113.  
  114.         /*
  115.          * Notify the address space from wich the ASID
  116.          * was stolen by invalidating its asid member.
  117.          */
  118.         as->asid = ASID_INVALID;
  119.         spinlock_unlock(&as->lock);
  120.  
  121.         /*
  122.          * Get the system rid of the stolen ASID.
  123.          */
  124.         tlb_shootdown_start(TLB_INVL_ASID, asid, 0, 0);
  125.         tlb_shootdown_finalize();
  126.         tlb_invalidate_asid(asid);
  127.     } else {
  128.  
  129.         /*
  130.          * There is at least one unallocated ASID.
  131.          * Find it and assign it.
  132.          */
  133.  
  134.         asid = asid_find_free();
  135.         asids_allocated++;
  136.     }
  137.    
  138.     spinlock_unlock(&asidlock);
  139.    
  140.     return asid;
  141. }
  142.  
  143. /** Release address space identifier.
  144.  *
  145.  * This code relies on architecture
  146.  * dependent functionality.
  147.  *
  148.  * @param asid ASID to be released.
  149.  */
  150. void asid_put(asid_t asid)
  151. {
  152.     ipl_t ipl;
  153.  
  154.     ipl = interrupts_disable();
  155.     spinlock_lock(&asidlock);
  156.  
  157.     asids_allocated--;
  158.     asid_put_arch(asid);
  159.    
  160.     spinlock_unlock(&asidlock);
  161.     interrupts_restore(ipl);
  162. }
  163.