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