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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.  * @file    asid.c
  31.  * @brief   ASID management.
  32.  *
  33.  * Modern processor architectures optimize TLB utilization
  34.  * by using ASIDs (a.k.a. memory contexts on sparc64 and
  35.  * region identifiers on ia64). These ASIDs help to associate
  36.  * each TLB item with an address space, thus making
  37.  * finer-grained TLB invalidation possible.
  38.  *
  39.  * Unfortunatelly, there are usually less ASIDs available than
  40.  * there can be unique as_t structures (i.e. address spaces
  41.  * recognized by the kernel).
  42.  *
  43.  * When system runs short of ASIDs, it will attempt to steal
  44.  * ASID from an address space that has not been active for
  45.  * a while.
  46.  *
  47.  * This code depends on the fact that ASIDS_ALLOCABLE
  48.  * is greater than number of supported CPUs (i.e. the
  49.  * amount of concurently active address spaces).
  50.  *
  51.  * Architectures that don't have hardware support for address
  52.  * spaces do not compile with this file.
  53.  */
  54.  
  55. #include <mm/asid.h>
  56. #include <mm/as.h>
  57. #include <mm/tlb.h>
  58. #include <arch/mm/asid.h>
  59. #include <synch/spinlock.h>
  60. #include <synch/mutex.h>
  61. #include <arch.h>
  62. #include <adt/list.h>
  63. #include <debug.h>
  64.  
  65. /**
  66.  * asidlock protects the asids_allocated counter.
  67.  */
  68. SPINLOCK_INITIALIZE(asidlock);
  69.  
  70. static count_t asids_allocated = 0;
  71.  
  72. /** Allocate free address space identifier.
  73.  *
  74.  * Interrupts must be disabled and as_lock must be held
  75.  * prior to this call
  76.  *
  77.  * @return New ASID.
  78.  */
  79. asid_t asid_get(void)
  80. {
  81.     asid_t asid;
  82.     link_t *tmp;
  83.     as_t *as;
  84.  
  85.     /*
  86.      * Check if there is an unallocated ASID.
  87.      */
  88.    
  89.     spinlock_lock(&asidlock);
  90.     if (asids_allocated == ASIDS_ALLOCABLE) {
  91.  
  92.         /*
  93.          * All ASIDs are already allocated.
  94.          * Resort to stealing.
  95.          */
  96.        
  97.         /*
  98.          * Remove the first item on the list.
  99.          * It is guaranteed to belong to an
  100.          * inactive address space.
  101.          */
  102.         ASSERT(!list_empty(&inactive_as_with_asid_head));
  103.         tmp = inactive_as_with_asid_head.next;
  104.         list_remove(tmp);
  105.        
  106.         as = list_get_instance(tmp, as_t, inactive_as_with_asid_link);
  107.         mutex_lock_active(&as->lock);
  108.  
  109.         /*
  110.          * Steal the ASID.
  111.          * Note that the stolen ASID is not active.
  112.          */
  113.         asid = as->asid;
  114.         ASSERT(asid != ASID_INVALID);
  115.  
  116.         /*
  117.          * Notify the address space from wich the ASID
  118.          * was stolen by invalidating its asid member.
  119.          */
  120.         as->asid = ASID_INVALID;
  121.         mutex_unlock(&as->lock);
  122.  
  123.         /*
  124.          * Get the system rid of the stolen ASID.
  125.          */
  126.         tlb_shootdown_start(TLB_INVL_ASID, asid, 0, 0);
  127.         tlb_shootdown_finalize();
  128.         tlb_invalidate_asid(asid);
  129.     } else {
  130.  
  131.         /*
  132.          * There is at least one unallocated ASID.
  133.          * Find it and assign it.
  134.          */
  135.  
  136.         asid = asid_find_free();
  137.         asids_allocated++;
  138.     }
  139.    
  140.     spinlock_unlock(&asidlock);
  141.    
  142.     return asid;
  143. }
  144.  
  145. /** Release address space identifier.
  146.  *
  147.  * This code relies on architecture
  148.  * dependent functionality.
  149.  *
  150.  * @param asid ASID to be released.
  151.  */
  152. void asid_put(asid_t asid)
  153. {
  154.     ipl_t ipl;
  155.  
  156.     ipl = interrupts_disable();
  157.     spinlock_lock(&asidlock);
  158.  
  159.     asids_allocated--;
  160.     asid_put_arch(asid);
  161.    
  162.     spinlock_unlock(&asidlock);
  163.     interrupts_restore(ipl);
  164. }
  165.