| 1 | /* $NetBSD: uvm_emap.c,v 1.11 2014/11/27 14:25:01 uebayasi Exp $ */ |
| 2 | |
| 3 | /*- |
| 4 | * Copyright (c) 2009, 2010 The NetBSD Foundation, Inc. |
| 5 | * All rights reserved. |
| 6 | * |
| 7 | * This code is derived from software contributed to The NetBSD Foundation |
| 8 | * by Mindaugas Rasiukevicius and Andrew Doran. |
| 9 | * |
| 10 | * Redistribution and use in source and binary forms, with or without |
| 11 | * modification, are permitted provided that the following conditions |
| 12 | * are met: |
| 13 | * 1. Redistributions of source code must retain the above copyright |
| 14 | * notice, this list of conditions and the following disclaimer. |
| 15 | * 2. Redistributions in binary form must reproduce the above copyright |
| 16 | * notice, this list of conditions and the following disclaimer in the |
| 17 | * documentation and/or other materials provided with the distribution. |
| 18 | * |
| 19 | * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS |
| 20 | * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
| 21 | * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
| 22 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS |
| 23 | * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| 24 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| 25 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| 26 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| 27 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| 28 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| 29 | * POSSIBILITY OF SUCH DAMAGE. |
| 30 | */ |
| 31 | |
| 32 | /* |
| 33 | * UVM ephemeral mapping interface. |
| 34 | */ |
| 35 | |
| 36 | /* |
| 37 | * Overview: |
| 38 | * |
| 39 | * On multiprocessor systems, frequent uses of pmap_kenter_pa/pmap_kremove |
| 40 | * for ephemeral mappings are not desirable because they likely involve |
| 41 | * TLB flush IPIs because that pmap_kernel() is shared among all LWPs. |
| 42 | * This interface can be used instead, to reduce the number of IPIs. |
| 43 | * |
| 44 | * For a single-page mapping, PMAP_DIRECT_MAP is likely a better choice |
| 45 | * if available. (__HAVE_DIRECT_MAP) |
| 46 | */ |
| 47 | |
| 48 | /* |
| 49 | * How to use: |
| 50 | * |
| 51 | * Map pages at the address: |
| 52 | * |
| 53 | * uvm_emap_enter(va, pgs, npages); |
| 54 | * gen = uvm_emap_produce(); |
| 55 | * |
| 56 | * Read pages via the mapping: |
| 57 | * |
| 58 | * uvm_emap_consume(gen); |
| 59 | * some_access(va); |
| 60 | * |
| 61 | * After finishing using the mapping: |
| 62 | * |
| 63 | * uvm_emap_remove(va, len); |
| 64 | */ |
| 65 | |
| 66 | /* |
| 67 | * Notes for pmap developers: |
| 68 | * |
| 69 | * Generic (more expensive) stubs are implemented for architectures which |
| 70 | * do not support pmap. |
| 71 | * |
| 72 | * Note that uvm_emap_update() is called from lower pmap(9) layer, while |
| 73 | * other functions call to pmap(9). Typical pattern of update in pmap: |
| 74 | * |
| 75 | * u_int gen = uvm_emap_gen_return(); |
| 76 | * tlbflush(); |
| 77 | * uvm_emap_update(); |
| 78 | * |
| 79 | * It is also used from IPI context, therefore functions must safe. |
| 80 | */ |
| 81 | |
| 82 | #include <sys/cdefs.h> |
| 83 | __KERNEL_RCSID(0, "$NetBSD: uvm_emap.c,v 1.11 2014/11/27 14:25:01 uebayasi Exp $" ); |
| 84 | |
| 85 | #include <sys/param.h> |
| 86 | #include <sys/kernel.h> |
| 87 | #include <sys/cpu.h> |
| 88 | #include <sys/atomic.h> |
| 89 | #include <sys/lwp.h> |
| 90 | #include <sys/vmem.h> |
| 91 | #include <sys/types.h> |
| 92 | |
| 93 | #include <uvm/uvm.h> |
| 94 | #include <uvm/uvm_extern.h> |
| 95 | |
| 96 | /* XXX: Arbitrary. */ |
| 97 | #ifdef _LP64 |
| 98 | #define UVM_EMAP_SIZE (128 * 1024 * 1024) /* 128 MB */ |
| 99 | #else |
| 100 | #define UVM_EMAP_SIZE (32 * 1024 * 1024) /* 32 MB */ |
| 101 | #endif |
| 102 | |
| 103 | static u_int _uvm_emap_gen[COHERENCY_UNIT - sizeof(u_int)] |
| 104 | __aligned(COHERENCY_UNIT); |
| 105 | |
| 106 | #define uvm_emap_gen (_uvm_emap_gen[0]) |
| 107 | |
| 108 | u_int uvm_emap_size = UVM_EMAP_SIZE; |
| 109 | static vaddr_t uvm_emap_va; |
| 110 | static vmem_t * uvm_emap_vmem; |
| 111 | |
| 112 | /* |
| 113 | * uvm_emap_init: initialize subsystem. |
| 114 | */ |
| 115 | void |
| 116 | uvm_emap_sysinit(void) |
| 117 | { |
| 118 | struct uvm_cpu *ucpu; |
| 119 | /* size_t qmax; */ |
| 120 | u_int i; |
| 121 | |
| 122 | uvm_emap_size = roundup(uvm_emap_size, PAGE_SIZE); |
| 123 | #if 0 |
| 124 | qmax = 16 * PAGE_SIZE; |
| 125 | uvm_emap_va = uvm_km_alloc(kernel_map, uvm_emap_size, 0, |
| 126 | UVM_KMF_VAONLY | UVM_KMF_WAITVA); |
| 127 | if (uvm_emap_va == 0) { |
| 128 | panic("uvm_emap_init: KVA allocation failed" ); |
| 129 | } |
| 130 | |
| 131 | uvm_emap_vmem = vmem_create("emap" , uvm_emap_va, uvm_emap_size, |
| 132 | PAGE_SIZE, NULL, NULL, NULL, qmax, VM_SLEEP, IPL_NONE); |
| 133 | if (uvm_emap_vmem == NULL) { |
| 134 | panic("uvm_emap_init: vmem creation failed" ); |
| 135 | } |
| 136 | #else |
| 137 | uvm_emap_va = 0; |
| 138 | uvm_emap_vmem = NULL; |
| 139 | #endif |
| 140 | /* Initial generation value is 1. */ |
| 141 | uvm_emap_gen = 1; |
| 142 | for (i = 0; i < maxcpus; i++) { |
| 143 | ucpu = uvm.cpus[i]; |
| 144 | if (ucpu != NULL) { |
| 145 | ucpu->emap_gen = 1; |
| 146 | } |
| 147 | } |
| 148 | } |
| 149 | |
| 150 | /* |
| 151 | * uvm_emap_alloc: allocate a window. |
| 152 | */ |
| 153 | vaddr_t |
| 154 | uvm_emap_alloc(vsize_t size, bool waitok) |
| 155 | { |
| 156 | vmem_addr_t addr; |
| 157 | |
| 158 | KASSERT(size > 0); |
| 159 | KASSERT(round_page(size) == size); |
| 160 | |
| 161 | if (vmem_alloc(uvm_emap_vmem, size, |
| 162 | VM_INSTANTFIT | (waitok ? VM_SLEEP : VM_NOSLEEP), &addr) == 0) |
| 163 | return (vaddr_t)addr; |
| 164 | |
| 165 | return (vaddr_t)0; |
| 166 | } |
| 167 | |
| 168 | /* |
| 169 | * uvm_emap_free: free a window. |
| 170 | */ |
| 171 | void |
| 172 | uvm_emap_free(vaddr_t va, size_t size) |
| 173 | { |
| 174 | |
| 175 | KASSERT(va >= uvm_emap_va); |
| 176 | KASSERT(size <= uvm_emap_size); |
| 177 | KASSERT(va + size <= uvm_emap_va + uvm_emap_size); |
| 178 | |
| 179 | vmem_free(uvm_emap_vmem, va, size); |
| 180 | } |
| 181 | |
| 182 | #ifdef __HAVE_PMAP_EMAP |
| 183 | |
| 184 | /* |
| 185 | * uvm_emap_enter: enter a new mapping, without TLB flush. |
| 186 | */ |
| 187 | void |
| 188 | uvm_emap_enter(vaddr_t va, struct vm_page **pgs, u_int npages) |
| 189 | { |
| 190 | paddr_t pa; |
| 191 | u_int n; |
| 192 | |
| 193 | for (n = 0; n < npages; n++, va += PAGE_SIZE) { |
| 194 | pa = VM_PAGE_TO_PHYS(pgs[n]); |
| 195 | pmap_emap_enter(va, pa, VM_PROT_READ); |
| 196 | } |
| 197 | } |
| 198 | |
| 199 | /* |
| 200 | * uvm_emap_remove: remove a mapping. |
| 201 | */ |
| 202 | void |
| 203 | uvm_emap_remove(vaddr_t sva, vsize_t len) |
| 204 | { |
| 205 | |
| 206 | pmap_emap_remove(sva, len); |
| 207 | } |
| 208 | |
| 209 | /* |
| 210 | * uvm_emap_gen_return: get the global generation number. |
| 211 | * |
| 212 | * => can be called from IPI handler, therefore function must be safe. |
| 213 | */ |
| 214 | u_int |
| 215 | uvm_emap_gen_return(void) |
| 216 | { |
| 217 | u_int gen; |
| 218 | |
| 219 | gen = uvm_emap_gen; |
| 220 | if (__predict_false(gen == UVM_EMAP_INACTIVE)) { |
| 221 | /* |
| 222 | * Instead of looping, just increase in our side. |
| 223 | * Other thread could race and increase it again, |
| 224 | * but without any negative effect. |
| 225 | */ |
| 226 | gen = atomic_inc_uint_nv(&uvm_emap_gen); |
| 227 | } |
| 228 | KASSERT(gen != UVM_EMAP_INACTIVE); |
| 229 | return gen; |
| 230 | } |
| 231 | |
| 232 | /* |
| 233 | * uvm_emap_switch: if the CPU is 'behind' the LWP in emap visibility, |
| 234 | * perform TLB flush and thus update the local view. Main purpose is |
| 235 | * to handle kernel preemption, while emap is in use. |
| 236 | * |
| 237 | * => called from mi_switch(), when LWP returns after block or preempt. |
| 238 | */ |
| 239 | void |
| 240 | uvm_emap_switch(lwp_t *l) |
| 241 | { |
| 242 | struct uvm_cpu *ucpu; |
| 243 | u_int curgen, gen; |
| 244 | |
| 245 | KASSERT(kpreempt_disabled()); |
| 246 | |
| 247 | /* If LWP did not use emap, then nothing to do. */ |
| 248 | if (__predict_true(l->l_emap_gen == UVM_EMAP_INACTIVE)) { |
| 249 | return; |
| 250 | } |
| 251 | |
| 252 | /* |
| 253 | * No need to synchronise if generation number of current CPU is |
| 254 | * newer than the number of this LWP. |
| 255 | * |
| 256 | * This test assumes two's complement arithmetic and allows |
| 257 | * ~2B missed updates before it will produce bad results. |
| 258 | */ |
| 259 | ucpu = curcpu()->ci_data.cpu_uvm; |
| 260 | curgen = ucpu->emap_gen; |
| 261 | gen = l->l_emap_gen; |
| 262 | if (__predict_true((signed int)(curgen - gen) >= 0)) { |
| 263 | return; |
| 264 | } |
| 265 | |
| 266 | /* |
| 267 | * See comments in uvm_emap_consume() about memory |
| 268 | * barriers and race conditions. |
| 269 | */ |
| 270 | curgen = uvm_emap_gen_return(); |
| 271 | pmap_emap_sync(false); |
| 272 | ucpu->emap_gen = curgen; |
| 273 | } |
| 274 | |
| 275 | /* |
| 276 | * uvm_emap_consume: update the current CPU and LWP to the given generation |
| 277 | * of the emap. In a case of LWP migration to a different CPU after block |
| 278 | * or preempt, uvm_emap_switch() will synchronise. |
| 279 | * |
| 280 | * => may be called from both interrupt and thread context. |
| 281 | */ |
| 282 | void |
| 283 | uvm_emap_consume(u_int gen) |
| 284 | { |
| 285 | struct cpu_info *ci; |
| 286 | struct uvm_cpu *ucpu; |
| 287 | lwp_t *l = curlwp; |
| 288 | u_int curgen; |
| 289 | |
| 290 | if (gen == UVM_EMAP_INACTIVE) { |
| 291 | return; |
| 292 | } |
| 293 | |
| 294 | /* |
| 295 | * No need to synchronise if generation number of current CPU is |
| 296 | * newer than the number of this LWP. |
| 297 | * |
| 298 | * This test assumes two's complement arithmetic and allows |
| 299 | * ~2B missed updates before it will produce bad results. |
| 300 | */ |
| 301 | kpreempt_disable(); |
| 302 | ci = l->l_cpu; |
| 303 | ucpu = ci->ci_data.cpu_uvm; |
| 304 | if (__predict_true((signed int)(ucpu->emap_gen - gen) >= 0)) { |
| 305 | l->l_emap_gen = ucpu->emap_gen; |
| 306 | kpreempt_enable(); |
| 307 | return; |
| 308 | } |
| 309 | |
| 310 | /* |
| 311 | * Record the current generation _before_ issuing the TLB flush. |
| 312 | * No need for a memory barrier before, as reading a stale value |
| 313 | * for uvm_emap_gen is not a problem. |
| 314 | * |
| 315 | * pmap_emap_sync() must implicitly perform a full memory barrier, |
| 316 | * which prevents us from fetching a value from after the TLB flush |
| 317 | * has occurred (which would be bad). |
| 318 | * |
| 319 | * We can race with an interrupt on the current CPU updating the |
| 320 | * counter to a newer value. This could cause us to set a stale |
| 321 | * value into ucpu->emap_gen, overwriting a newer update from the |
| 322 | * interrupt. However, it does not matter since: |
| 323 | * (1) Interrupts always run to completion or block. |
| 324 | * (2) Interrupts will only ever install a newer value and, |
| 325 | * (3) We will roll the value forward later. |
| 326 | */ |
| 327 | curgen = uvm_emap_gen_return(); |
| 328 | pmap_emap_sync(true); |
| 329 | ucpu->emap_gen = curgen; |
| 330 | l->l_emap_gen = curgen; |
| 331 | KASSERT((signed int)(curgen - gen) >= 0); |
| 332 | kpreempt_enable(); |
| 333 | } |
| 334 | |
| 335 | /* |
| 336 | * uvm_emap_produce: increment emap generation counter. |
| 337 | * |
| 338 | * => pmap updates must be globally visible. |
| 339 | * => caller must have already entered mappings. |
| 340 | * => may be called from both interrupt and thread context. |
| 341 | */ |
| 342 | u_int |
| 343 | uvm_emap_produce(void) |
| 344 | { |
| 345 | u_int gen; |
| 346 | again: |
| 347 | gen = atomic_inc_uint_nv(&uvm_emap_gen); |
| 348 | if (__predict_false(gen == UVM_EMAP_INACTIVE)) { |
| 349 | goto again; |
| 350 | } |
| 351 | return gen; |
| 352 | } |
| 353 | |
| 354 | /* |
| 355 | * uvm_emap_update: update global emap generation number for current CPU. |
| 356 | * |
| 357 | * Function is called by MD code (eg. pmap) to take advantage of TLB flushes |
| 358 | * initiated for other reasons, that sync the emap as a side effect. Note |
| 359 | * update should be performed before the actual TLB flush, to avoid race |
| 360 | * with newly generated number. |
| 361 | * |
| 362 | * => can be called from IPI handler, therefore function must be safe. |
| 363 | * => should be called _after_ TLB flush. |
| 364 | * => emap generation number should be taken _before_ TLB flush. |
| 365 | * => must be called with preemption disabled. |
| 366 | */ |
| 367 | void |
| 368 | uvm_emap_update(u_int gen) |
| 369 | { |
| 370 | struct uvm_cpu *ucpu; |
| 371 | |
| 372 | /* |
| 373 | * See comments in uvm_emap_consume() about memory barriers and |
| 374 | * race conditions. Store is atomic if emap_gen size is word. |
| 375 | */ |
| 376 | CTASSERT(sizeof(ucpu->emap_gen) == sizeof(int)); |
| 377 | /* XXX: KASSERT(kpreempt_disabled()); */ |
| 378 | |
| 379 | ucpu = curcpu()->ci_data.cpu_uvm; |
| 380 | ucpu->emap_gen = gen; |
| 381 | } |
| 382 | |
| 383 | #else |
| 384 | |
| 385 | /* |
| 386 | * Stubs for architectures which do not support emap. |
| 387 | */ |
| 388 | |
| 389 | void |
| 390 | uvm_emap_enter(vaddr_t va, struct vm_page **pgs, u_int npages) |
| 391 | { |
| 392 | paddr_t pa; |
| 393 | u_int n; |
| 394 | |
| 395 | for (n = 0; n < npages; n++, va += PAGE_SIZE) { |
| 396 | pa = VM_PAGE_TO_PHYS(pgs[n]); |
| 397 | pmap_kenter_pa(va, pa, VM_PROT_READ, 0); |
| 398 | } |
| 399 | pmap_update(pmap_kernel()); |
| 400 | } |
| 401 | |
| 402 | void |
| 403 | uvm_emap_remove(vaddr_t sva, vsize_t len) |
| 404 | { |
| 405 | |
| 406 | pmap_kremove(sva, len); |
| 407 | pmap_update(pmap_kernel()); |
| 408 | } |
| 409 | |
| 410 | #endif |
| 411 | |