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| 727 | jermar | 1 | /* |
| 2 | * Copyright (C) 2006 Jakub Jermar |
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| 3 | * All rights reserved. |
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| 4 | * |
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| 5 | * Redistribution and use in source and binary forms, with or without |
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| 6 | * modification, are permitted provided that the following conditions |
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| 7 | * are met: |
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| 8 | * |
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| 9 | * - Redistributions of source code must retain the above copyright |
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| 10 | * notice, this list of conditions and the following disclaimer. |
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| 11 | * - Redistributions in binary form must reproduce the above copyright |
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| 12 | * notice, this list of conditions and the following disclaimer in the |
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| 13 | * documentation and/or other materials provided with the distribution. |
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| 14 | * - The name of the author may not be used to endorse or promote products |
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| 15 | * derived from this software without specific prior written permission. |
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| 16 | * |
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| 17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
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| 18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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| 19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
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| 20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
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| 21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
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| 22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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| 23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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| 24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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| 25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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| 26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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| 27 | */ |
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| 28 | |||
| 29 | /* |
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| 30 | * ASID management. |
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| 31 | * |
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| 32 | * Modern processor architectures optimize TLB utilization |
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| 33 | * by using ASIDs (a.k.a. memory contexts on sparc64 and |
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| 34 | * region identifiers on ia64). These ASIDs help to associate |
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| 35 | * each TLB item with an address space, thus making |
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| 36 | * finer-grained TLB invalidation possible. |
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| 37 | * |
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| 38 | * Unfortunatelly, there are usually less ASIDs available than |
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| 39 | * there can be unique as_t structures (i.e. address spaces |
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| 40 | * recognized by the kernel). |
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| 41 | * |
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| 42 | * When system runs short of ASIDs, it will attempt to steal |
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| 43 | * ASID from an address space that has not been active for |
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| 44 | * a while. |
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| 45 | * |
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| 46 | * Architectures that don't have hardware support for address |
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| 47 | * spaces do not compile with this file. |
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| 48 | */ |
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| 49 | |||
| 50 | #include <mm/asid.h> |
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| 51 | #include <mm/as.h> |
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| 52 | #include <mm/tlb.h> |
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| 53 | #include <arch/mm/asid.h> |
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| 54 | #include <synch/spinlock.h> |
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| 55 | #include <arch.h> |
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| 56 | #include <list.h> |
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| 57 | #include <debug.h> |
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| 58 | |||
| 59 | /** |
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| 60 | * asidlock protects both the asids_allocated counter |
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| 61 | * and the list of address spaces that were already |
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| 62 | * assigned ASID. |
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| 63 | */ |
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| 64 | SPINLOCK_INITIALIZE(asidlock); |
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| 65 | |||
| 66 | static count_t asids_allocated = 0; |
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| 67 | |||
| 68 | /** |
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| 69 | * List of address spaces with assigned ASID. |
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| 70 | * When the system runs short of allocable |
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| 71 | * ASIDS, inactive address spaces are guaranteed |
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| 72 | * to be at the beginning of the list. |
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| 73 | */ |
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| 74 | LIST_INITIALIZE(as_with_asid_head); |
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| 75 | |||
| 76 | |||
| 77 | /** Allocate free address space identifier. |
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| 78 | * |
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| 79 | * This code depends on the fact that ASIDS_ALLOCABLE |
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| 80 | * is greater than number of supported CPUs. |
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| 81 | * |
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| 82 | * @return New ASID. |
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| 83 | */ |
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| 84 | asid_t asid_get(void) |
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| 85 | { |
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| 86 | ipl_t ipl; |
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| 87 | asid_t asid; |
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| 88 | link_t *tmp; |
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| 89 | as_t *as; |
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| 90 | |||
| 91 | /* |
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| 92 | * Check if there is an unallocated ASID. |
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| 93 | */ |
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| 94 | |||
| 95 | ipl = interrupts_disable(); |
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| 96 | spinlock_lock(&asidlock); |
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| 97 | if (asids_allocated == ASIDS_ALLOCABLE) { |
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| 98 | |||
| 99 | /* |
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| 100 | * All ASIDs are already allocated. |
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| 101 | * Resort to stealing. |
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| 102 | */ |
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| 103 | |||
| 104 | /* |
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| 105 | * Remove the first item on the list. |
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| 106 | * It is guaranteed to belong to an |
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| 107 | * inactive address space. |
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| 108 | */ |
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| 109 | tmp = as_with_asid_head.next; |
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| 110 | ASSERT(tmp != &as_with_asid_head); |
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| 111 | list_remove(tmp); |
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| 112 | |||
| 113 | as = list_get_instance(tmp, as_t, as_with_asid_link); |
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| 114 | spinlock_lock(&as->lock); |
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| 115 | |||
| 116 | /* |
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| 117 | * Steal the ASID. |
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| 118 | * Note that the stolen ASID is not active. |
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| 119 | */ |
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| 120 | asid = as->asid; |
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| 121 | ASSERT(asid != ASID_INVALID); |
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| 122 | |||
| 123 | /* |
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| 124 | * Get the system rid of the stolen ASID. |
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| 125 | */ |
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| 126 | tlb_shootdown_start(TLB_INVL_ASID, asid, 0, 0); |
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| 127 | tlb_shootdown_finalize(); |
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| 740 | jermar | 128 | tlb_invalidate_asid(asid); |
| 727 | jermar | 129 | as->asid = ASID_INVALID; |
| 130 | |||
| 131 | spinlock_unlock(&as->lock); |
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| 132 | } else { |
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| 133 | |||
| 134 | /* |
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| 135 | * There is at least one unallocated ASID. |
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| 136 | * Find it and assign it. |
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| 137 | */ |
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| 138 | |||
| 139 | asid = asid_find_free(); |
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| 140 | asids_allocated++; |
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| 141 | } |
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| 142 | |||
| 143 | spinlock_unlock(&asidlock); |
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| 144 | interrupts_restore(ipl); |
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| 145 | |||
| 146 | return asid; |
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| 147 | } |
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| 148 | |||
| 149 | /** Release address space identifier. |
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| 150 | * |
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| 151 | * This code relies on architecture |
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| 152 | * dependent functionality. |
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| 153 | * |
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| 154 | * @param asid ASID to be released. |
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| 155 | */ |
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| 156 | void asid_put(asid_t asid) |
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| 157 | { |
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| 158 | ipl_t ipl; |
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| 159 | |||
| 160 | ipl = interrupts_disable(); |
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| 161 | spinlock_lock(&asidlock); |
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| 162 | |||
| 163 | asids_allocated--; |
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| 164 | asid_put_arch(asid); |
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| 165 | |||
| 166 | spinlock_unlock(&asidlock); |
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| 167 | interrupts_restore(ipl); |
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| 168 | } |
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| 169 | |||
| 170 | /** Install ASID. |
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| 171 | * |
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| 172 | * This function is to be executed on each address space switch. |
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| 173 | * |
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| 174 | * @param as Address space. |
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| 175 | */ |
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| 176 | void asid_install(as_t *as) |
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| 177 | { |
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| 178 | ipl_t ipl; |
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| 179 | |||
| 180 | ipl = interrupts_disable(); |
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| 181 | spinlock_lock(&asidlock); |
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| 182 | spinlock_lock(&as->lock); |
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| 183 | |||
| 184 | if (as->asid != ASID_KERNEL) { |
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| 185 | if (as->asid != ASID_INVALID) { |
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| 186 | /* |
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| 187 | * This address space has valid ASID. |
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| 188 | * Remove 'as' from the list of address spaces |
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| 189 | * with assigned ASID, so that it can be later |
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| 190 | * appended to the tail of the same list. |
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| 191 | * This is to prevent stealing of ASIDs from |
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| 192 | * recently installed address spaces. |
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| 193 | */ |
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| 194 | list_remove(&as->as_with_asid_link); |
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| 195 | } else { |
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| 196 | spinlock_unlock(&as->lock); |
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| 197 | spinlock_unlock(&asidlock); |
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| 198 | |||
| 199 | /* |
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| 200 | * This address space doesn't have ASID assigned. |
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| 201 | * It was stolen or the address space is being |
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| 202 | * installed for the first time. |
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| 203 | * Allocate new ASID for it. |
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| 204 | */ |
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| 205 | as->asid = asid_get(); |
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| 206 | spinlock_lock(&asidlock); |
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| 207 | spinlock_lock(&as->lock); |
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| 208 | } |
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| 209 | |||
| 210 | /* |
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| 211 | * Now it is sure that 'as' has ASID. |
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| 212 | * It is therefore appended to the list |
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| 213 | * of address spaces from which it can |
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| 214 | * be stolen. |
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| 215 | */ |
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| 216 | list_append(&as->as_with_asid_link, &as_with_asid_head); |
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| 217 | } |
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| 218 | |||
| 219 | spinlock_unlock(&as->lock); |
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| 220 | spinlock_unlock(&asidlock); |
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| 221 | interrupts_restore(ipl); |
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| 222 | } |