1 /* 2 * Copyright 2014 IBM Corp. 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU General Public License 6 * as published by the Free Software Foundation; either version 7 * 2 of the License, or (at your option) any later version. 8 */ 9 10 #include <linux/workqueue.h> 11 #include <linux/sched/signal.h> 12 #include <linux/sched/mm.h> 13 #include <linux/pid.h> 14 #include <linux/mm.h> 15 #include <linux/moduleparam.h> 16 17 #undef MODULE_PARAM_PREFIX 18 #define MODULE_PARAM_PREFIX "cxl" "." 19 #include <asm/current.h> 20 #include <asm/copro.h> 21 #include <asm/mmu.h> 22 23 #include "cxl.h" 24 #include "trace.h" 25 26 static bool sste_matches(struct cxl_sste *sste, struct copro_slb *slb) 27 { 28 return ((sste->vsid_data == cpu_to_be64(slb->vsid)) && 29 (sste->esid_data == cpu_to_be64(slb->esid))); 30 } 31 32 /* 33 * This finds a free SSTE for the given SLB, or returns NULL if it's already in 34 * the segment table. 35 */ 36 static struct cxl_sste* find_free_sste(struct cxl_context *ctx, 37 struct copro_slb *slb) 38 { 39 struct cxl_sste *primary, *sste, *ret = NULL; 40 unsigned int mask = (ctx->sst_size >> 7) - 1; /* SSTP0[SegTableSize] */ 41 unsigned int entry; 42 unsigned int hash; 43 44 if (slb->vsid & SLB_VSID_B_1T) 45 hash = (slb->esid >> SID_SHIFT_1T) & mask; 46 else /* 256M */ 47 hash = (slb->esid >> SID_SHIFT) & mask; 48 49 primary = ctx->sstp + (hash << 3); 50 51 for (entry = 0, sste = primary; entry < 8; entry++, sste++) { 52 if (!ret && !(be64_to_cpu(sste->esid_data) & SLB_ESID_V)) 53 ret = sste; 54 if (sste_matches(sste, slb)) 55 return NULL; 56 } 57 if (ret) 58 return ret; 59 60 /* Nothing free, select an entry to cast out */ 61 ret = primary + ctx->sst_lru; 62 ctx->sst_lru = (ctx->sst_lru + 1) & 0x7; 63 64 return ret; 65 } 66 67 static void cxl_load_segment(struct cxl_context *ctx, struct copro_slb *slb) 68 { 69 /* mask is the group index, we search primary and secondary here. */ 70 struct cxl_sste *sste; 71 unsigned long flags; 72 73 spin_lock_irqsave(&ctx->sste_lock, flags); 74 sste = find_free_sste(ctx, slb); 75 if (!sste) 76 goto out_unlock; 77 78 pr_devel("CXL Populating SST[%li]: %#llx %#llx\n", 79 sste - ctx->sstp, slb->vsid, slb->esid); 80 trace_cxl_ste_write(ctx, sste - ctx->sstp, slb->esid, slb->vsid); 81 82 sste->vsid_data = cpu_to_be64(slb->vsid); 83 sste->esid_data = cpu_to_be64(slb->esid); 84 out_unlock: 85 spin_unlock_irqrestore(&ctx->sste_lock, flags); 86 } 87 88 static int cxl_fault_segment(struct cxl_context *ctx, struct mm_struct *mm, 89 u64 ea) 90 { 91 struct copro_slb slb = {0,0}; 92 int rc; 93 94 if (!(rc = copro_calculate_slb(mm, ea, &slb))) { 95 cxl_load_segment(ctx, &slb); 96 } 97 98 return rc; 99 } 100 101 static void cxl_ack_ae(struct cxl_context *ctx) 102 { 103 unsigned long flags; 104 105 cxl_ops->ack_irq(ctx, CXL_PSL_TFC_An_AE, 0); 106 107 spin_lock_irqsave(&ctx->lock, flags); 108 ctx->pending_fault = true; 109 ctx->fault_addr = ctx->dar; 110 ctx->fault_dsisr = ctx->dsisr; 111 spin_unlock_irqrestore(&ctx->lock, flags); 112 113 wake_up_all(&ctx->wq); 114 } 115 116 static int cxl_handle_segment_miss(struct cxl_context *ctx, 117 struct mm_struct *mm, u64 ea) 118 { 119 int rc; 120 121 pr_devel("CXL interrupt: Segment fault pe: %i ea: %#llx\n", ctx->pe, ea); 122 trace_cxl_ste_miss(ctx, ea); 123 124 if ((rc = cxl_fault_segment(ctx, mm, ea))) 125 cxl_ack_ae(ctx); 126 else { 127 128 mb(); /* Order seg table write to TFC MMIO write */ 129 cxl_ops->ack_irq(ctx, CXL_PSL_TFC_An_R, 0); 130 } 131 132 return IRQ_HANDLED; 133 } 134 135 static void cxl_handle_page_fault(struct cxl_context *ctx, 136 struct mm_struct *mm, u64 dsisr, u64 dar) 137 { 138 unsigned flt = 0; 139 int result; 140 unsigned long access, flags, inv_flags = 0; 141 142 trace_cxl_pte_miss(ctx, dsisr, dar); 143 144 if ((result = copro_handle_mm_fault(mm, dar, dsisr, &flt))) { 145 pr_devel("copro_handle_mm_fault failed: %#x\n", result); 146 return cxl_ack_ae(ctx); 147 } 148 149 /* 150 * update_mmu_cache() will not have loaded the hash since current->trap 151 * is not a 0x400 or 0x300, so just call hash_page_mm() here. 152 */ 153 access = _PAGE_PRESENT | _PAGE_READ; 154 if (dsisr & CXL_PSL_DSISR_An_S) 155 access |= _PAGE_WRITE; 156 157 access |= _PAGE_PRIVILEGED; 158 if ((!ctx->kernel) || (REGION_ID(dar) == USER_REGION_ID)) 159 access &= ~_PAGE_PRIVILEGED; 160 161 if (dsisr & DSISR_NOHPTE) 162 inv_flags |= HPTE_NOHPTE_UPDATE; 163 164 local_irq_save(flags); 165 hash_page_mm(mm, dar, access, 0x300, inv_flags); 166 local_irq_restore(flags); 167 168 pr_devel("Page fault successfully handled for pe: %i!\n", ctx->pe); 169 cxl_ops->ack_irq(ctx, CXL_PSL_TFC_An_R, 0); 170 } 171 172 /* 173 * Returns the mm_struct corresponding to the context ctx via ctx->pid 174 * In case the task has exited we use the task group leader accessible 175 * via ctx->glpid to find the next task in the thread group that has a 176 * valid mm_struct associated with it. If a task with valid mm_struct 177 * is found the ctx->pid is updated to use the task struct for subsequent 178 * translations. In case no valid mm_struct is found in the task group to 179 * service the fault a NULL is returned. 180 */ 181 static struct mm_struct *get_mem_context(struct cxl_context *ctx) 182 { 183 struct task_struct *task = NULL; 184 struct mm_struct *mm = NULL; 185 struct pid *old_pid = ctx->pid; 186 187 if (old_pid == NULL) { 188 pr_warn("%s: Invalid context for pe=%d\n", 189 __func__, ctx->pe); 190 return NULL; 191 } 192 193 task = get_pid_task(old_pid, PIDTYPE_PID); 194 195 /* 196 * pid_alive may look racy but this saves us from costly 197 * get_task_mm when the task is a zombie. In worst case 198 * we may think a task is alive, which is about to die 199 * but get_task_mm will return NULL. 200 */ 201 if (task != NULL && pid_alive(task)) 202 mm = get_task_mm(task); 203 204 /* release the task struct that was taken earlier */ 205 if (task) 206 put_task_struct(task); 207 else 208 pr_devel("%s: Context owning pid=%i for pe=%i dead\n", 209 __func__, pid_nr(old_pid), ctx->pe); 210 211 /* 212 * If we couldn't find the mm context then use the group 213 * leader to iterate over the task group and find a task 214 * that gives us mm_struct. 215 */ 216 if (unlikely(mm == NULL && ctx->glpid != NULL)) { 217 218 rcu_read_lock(); 219 task = pid_task(ctx->glpid, PIDTYPE_PID); 220 if (task) 221 do { 222 mm = get_task_mm(task); 223 if (mm) { 224 ctx->pid = get_task_pid(task, 225 PIDTYPE_PID); 226 break; 227 } 228 task = next_thread(task); 229 } while (task && !thread_group_leader(task)); 230 rcu_read_unlock(); 231 232 /* check if we switched pid */ 233 if (ctx->pid != old_pid) { 234 if (mm) 235 pr_devel("%s:pe=%i switch pid %i->%i\n", 236 __func__, ctx->pe, pid_nr(old_pid), 237 pid_nr(ctx->pid)); 238 else 239 pr_devel("%s:Cannot find mm for pid=%i\n", 240 __func__, pid_nr(old_pid)); 241 242 /* drop the reference to older pid */ 243 put_pid(old_pid); 244 } 245 } 246 247 return mm; 248 } 249 250 251 252 void cxl_handle_fault(struct work_struct *fault_work) 253 { 254 struct cxl_context *ctx = 255 container_of(fault_work, struct cxl_context, fault_work); 256 u64 dsisr = ctx->dsisr; 257 u64 dar = ctx->dar; 258 struct mm_struct *mm = NULL; 259 260 if (cpu_has_feature(CPU_FTR_HVMODE)) { 261 if (cxl_p2n_read(ctx->afu, CXL_PSL_DSISR_An) != dsisr || 262 cxl_p2n_read(ctx->afu, CXL_PSL_DAR_An) != dar || 263 cxl_p2n_read(ctx->afu, CXL_PSL_PEHandle_An) != ctx->pe) { 264 /* Most likely explanation is harmless - a dedicated 265 * process has detached and these were cleared by the 266 * PSL purge, but warn about it just in case 267 */ 268 dev_notice(&ctx->afu->dev, "cxl_handle_fault: Translation fault regs changed\n"); 269 return; 270 } 271 } 272 273 /* Early return if the context is being / has been detached */ 274 if (ctx->status == CLOSED) { 275 cxl_ack_ae(ctx); 276 return; 277 } 278 279 pr_devel("CXL BOTTOM HALF handling fault for afu pe: %i. " 280 "DSISR: %#llx DAR: %#llx\n", ctx->pe, dsisr, dar); 281 282 if (!ctx->kernel) { 283 284 mm = get_mem_context(ctx); 285 /* indicates all the thread in task group have exited */ 286 if (mm == NULL) { 287 pr_devel("%s: unable to get mm for pe=%d pid=%i\n", 288 __func__, ctx->pe, pid_nr(ctx->pid)); 289 cxl_ack_ae(ctx); 290 return; 291 } else { 292 pr_devel("Handling page fault for pe=%d pid=%i\n", 293 ctx->pe, pid_nr(ctx->pid)); 294 } 295 } 296 297 if (dsisr & CXL_PSL_DSISR_An_DS) 298 cxl_handle_segment_miss(ctx, mm, dar); 299 else if (dsisr & CXL_PSL_DSISR_An_DM) 300 cxl_handle_page_fault(ctx, mm, dsisr, dar); 301 else 302 WARN(1, "cxl_handle_fault has nothing to handle\n"); 303 304 if (mm) 305 mmput(mm); 306 } 307 308 static void cxl_prefault_one(struct cxl_context *ctx, u64 ea) 309 { 310 struct mm_struct *mm; 311 312 mm = get_mem_context(ctx); 313 if (mm == NULL) { 314 pr_devel("cxl_prefault_one unable to get mm %i\n", 315 pid_nr(ctx->pid)); 316 return; 317 } 318 319 cxl_fault_segment(ctx, mm, ea); 320 321 mmput(mm); 322 } 323 324 static u64 next_segment(u64 ea, u64 vsid) 325 { 326 if (vsid & SLB_VSID_B_1T) 327 ea |= (1ULL << 40) - 1; 328 else 329 ea |= (1ULL << 28) - 1; 330 331 return ea + 1; 332 } 333 334 static void cxl_prefault_vma(struct cxl_context *ctx) 335 { 336 u64 ea, last_esid = 0; 337 struct copro_slb slb; 338 struct vm_area_struct *vma; 339 int rc; 340 struct mm_struct *mm; 341 342 mm = get_mem_context(ctx); 343 if (mm == NULL) { 344 pr_devel("cxl_prefault_vm unable to get mm %i\n", 345 pid_nr(ctx->pid)); 346 return; 347 } 348 349 down_read(&mm->mmap_sem); 350 for (vma = mm->mmap; vma; vma = vma->vm_next) { 351 for (ea = vma->vm_start; ea < vma->vm_end; 352 ea = next_segment(ea, slb.vsid)) { 353 rc = copro_calculate_slb(mm, ea, &slb); 354 if (rc) 355 continue; 356 357 if (last_esid == slb.esid) 358 continue; 359 360 cxl_load_segment(ctx, &slb); 361 last_esid = slb.esid; 362 } 363 } 364 up_read(&mm->mmap_sem); 365 366 mmput(mm); 367 } 368 369 void cxl_prefault(struct cxl_context *ctx, u64 wed) 370 { 371 switch (ctx->afu->prefault_mode) { 372 case CXL_PREFAULT_WED: 373 cxl_prefault_one(ctx, wed); 374 break; 375 case CXL_PREFAULT_ALL: 376 cxl_prefault_vma(ctx); 377 break; 378 default: 379 break; 380 } 381 } 382