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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. /** @addtogroup genarchmm
  30.  * @{
  31.  */
  32.  
  33. /**
  34.  * @file
  35.  * @brief ASID management.
  36.  *
  37.  * Modern processor architectures optimize TLB utilization
  38.  * by using ASIDs (a.k.a. memory contexts on sparc64 and
  39.  * region identifiers on ia64). These ASIDs help to associate
  40.  * each TLB item with an address space, thus making
  41.  * finer-grained TLB invalidation possible.
  42.  *
  43.  * Unfortunatelly, there are usually less ASIDs available than
  44.  * there can be unique as_t structures (i.e. address spaces
  45.  * recognized by the kernel).
  46.  *
  47.  * When system runs short of ASIDs, it will attempt to steal
  48.  * ASID from an address space that has not been active for
  49.  * a while.
  50.  *
  51.  * This code depends on the fact that ASIDS_ALLOCABLE
  52.  * is greater than number of supported CPUs (i.e. the
  53.  * amount of concurently active address spaces).
  54.  *
  55.  * Architectures that don't have hardware support for address
  56.  * spaces do not compile with this file.
  57.  */
  58.  
  59. #include <mm/asid.h>
  60. #include <mm/as.h>
  61. #include <mm/tlb.h>
  62. #include <arch/mm/asid.h>
  63. #include <synch/spinlock.h>
  64. #include <synch/mutex.h>
  65. #include <adt/list.h>
  66. #include <debug.h>
  67.  
  68. static size_t asids_allocated = 0;
  69.  
  70. /** Allocate free address space identifier.
  71.  *
  72.  * Interrupts must be disabled and inactive_as_with_asid_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.     if (asids_allocated == ASIDS_ALLOCABLE) {
  88.  
  89.         /*
  90.          * All ASIDs are already allocated.
  91.          * Resort to stealing.
  92.          */
  93.        
  94.         /*
  95.          * Remove the first item on the list.
  96.          * It is guaranteed to belong to an
  97.          * inactive address space.
  98.          */
  99.         ASSERT(!list_empty(&inactive_as_with_asid_head));
  100.         tmp = inactive_as_with_asid_head.next;
  101.         list_remove(tmp);
  102.        
  103.         as = list_get_instance(tmp, as_t, inactive_as_with_asid_link);
  104.  
  105.         /*
  106.          * Steal the ASID.
  107.          * Note that the stolen ASID is not active.
  108.          */
  109.         asid = as->asid;
  110.         ASSERT(asid != ASID_INVALID);
  111.  
  112.         /*
  113.          * Notify the address space from wich the ASID
  114.          * was stolen by invalidating its asid member.
  115.          */
  116.         as->asid = ASID_INVALID;
  117.        
  118.         /*
  119.          * If the architecture uses some software cache
  120.          * of TLB entries (e.g. TSB on sparc64), the
  121.          * cache must be invalidated as well.
  122.          */
  123.         as_invalidate_translation_cache(as, 0, (size_t) -1);
  124.        
  125.         /*
  126.          * Get the system rid of the stolen ASID.
  127.          */
  128.         tlb_shootdown_start(TLB_INVL_ASID, asid, 0, 0);
  129.         tlb_invalidate_asid(asid);
  130.         tlb_shootdown_finalize();
  131.     } else {
  132.  
  133.         /*
  134.          * There is at least one unallocated ASID.
  135.          * Find it and assign it.
  136.          */
  137.  
  138.         asid = asid_find_free();
  139.         asids_allocated++;
  140.  
  141.         /*
  142.          * Purge the allocated ASID from TLBs.
  143.          */
  144.         tlb_shootdown_start(TLB_INVL_ASID, asid, 0, 0);
  145.         tlb_invalidate_asid(asid);
  146.         tlb_shootdown_finalize();
  147.     }
  148.    
  149.     return asid;
  150. }
  151.  
  152. /** Release address space identifier.
  153.  *
  154.  * This code relies on architecture
  155.  * dependent functionality.
  156.  *
  157.  * @param asid ASID to be released.
  158.  */
  159. void asid_put(asid_t asid)
  160. {
  161.     asids_allocated--;
  162.     asid_put_arch(asid);
  163. }
  164.  
  165. /** @}
  166.  */
  167.