root/drivers/misc/cxl/fault.c

DEFINITIONS

1. sste_matches
2. find_free_sste
3. cxl_load_segment
4. cxl_fault_segment
5. cxl_ack_ae
6. cxl_handle_segment_miss
7. cxl_handle_mm_fault
8. cxl_handle_page_fault
9. get_mem_context
10. cxl_is_segment_miss
11. cxl_is_page_fault
12. cxl_handle_fault
13. cxl_prefault_one
14. next_segment
15. cxl_prefault_vma
16. cxl_prefault

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright 2014 IBM Corp.
   4  */
   5 
   6 #include <linux/workqueue.h>
   7 #include <linux/sched/signal.h>
   8 #include <linux/sched/mm.h>
   9 #include <linux/pid.h>
  10 #include <linux/mm.h>
  11 #include <linux/moduleparam.h>
  12 
  13 #undef MODULE_PARAM_PREFIX
  14 #define MODULE_PARAM_PREFIX "cxl" "."
  15 #include <asm/current.h>
  16 #include <asm/copro.h>
  17 #include <asm/mmu.h>
  18 
  19 #include "cxl.h"
  20 #include "trace.h"
  21 
  22 static bool sste_matches(struct cxl_sste *sste, struct copro_slb *slb)
  23 {
  24         return ((sste->vsid_data == cpu_to_be64(slb->vsid)) &&
  25                 (sste->esid_data == cpu_to_be64(slb->esid)));
  26 }
  27 
  28 /*
  29  * This finds a free SSTE for the given SLB, or returns NULL if it's already in
  30  * the segment table.
  31  */
  32 static struct cxl_sste *find_free_sste(struct cxl_context *ctx,
  33                                        struct copro_slb *slb)
  34 {
  35         struct cxl_sste *primary, *sste, *ret = NULL;
  36         unsigned int mask = (ctx->sst_size >> 7) - 1; /* SSTP0[SegTableSize] */
  37         unsigned int entry;
  38         unsigned int hash;
  39 
  40         if (slb->vsid & SLB_VSID_B_1T)
  41                 hash = (slb->esid >> SID_SHIFT_1T) & mask;
  42         else /* 256M */
  43                 hash = (slb->esid >> SID_SHIFT) & mask;
  44 
  45         primary = ctx->sstp + (hash << 3);
  46 
  47         for (entry = 0, sste = primary; entry < 8; entry++, sste++) {
  48                 if (!ret && !(be64_to_cpu(sste->esid_data) & SLB_ESID_V))
  49                         ret = sste;
  50                 if (sste_matches(sste, slb))
  51                         return NULL;
  52         }
  53         if (ret)
  54                 return ret;
  55 
  56         /* Nothing free, select an entry to cast out */
  57         ret = primary + ctx->sst_lru;
  58         ctx->sst_lru = (ctx->sst_lru + 1) & 0x7;
  59 
  60         return ret;
  61 }
  62 
  63 static void cxl_load_segment(struct cxl_context *ctx, struct copro_slb *slb)
  64 {
  65         /* mask is the group index, we search primary and secondary here. */
  66         struct cxl_sste *sste;
  67         unsigned long flags;
  68 
  69         spin_lock_irqsave(&ctx->sste_lock, flags);
  70         sste = find_free_sste(ctx, slb);
  71         if (!sste)
  72                 goto out_unlock;
  73 
  74         pr_devel("CXL Populating SST[%li]: %#llx %#llx\n",
  75                         sste - ctx->sstp, slb->vsid, slb->esid);
  76         trace_cxl_ste_write(ctx, sste - ctx->sstp, slb->esid, slb->vsid);
  77 
  78         sste->vsid_data = cpu_to_be64(slb->vsid);
  79         sste->esid_data = cpu_to_be64(slb->esid);
  80 out_unlock:
  81         spin_unlock_irqrestore(&ctx->sste_lock, flags);
  82 }
  83 
  84 static int cxl_fault_segment(struct cxl_context *ctx, struct mm_struct *mm,
  85                              u64 ea)
  86 {
  87         struct copro_slb slb = {0,0};
  88         int rc;
  89 
  90         if (!(rc = copro_calculate_slb(mm, ea, &slb))) {
  91                 cxl_load_segment(ctx, &slb);
  92         }
  93 
  94         return rc;
  95 }
  96 
  97 static void cxl_ack_ae(struct cxl_context *ctx)
  98 {
  99         unsigned long flags;
 100 
 101         cxl_ops->ack_irq(ctx, CXL_PSL_TFC_An_AE, 0);
 102 
 103         spin_lock_irqsave(&ctx->lock, flags);
 104         ctx->pending_fault = true;
 105         ctx->fault_addr = ctx->dar;
 106         ctx->fault_dsisr = ctx->dsisr;
 107         spin_unlock_irqrestore(&ctx->lock, flags);
 108 
 109         wake_up_all(&ctx->wq);
 110 }
 111 
 112 static int cxl_handle_segment_miss(struct cxl_context *ctx,
 113                                    struct mm_struct *mm, u64 ea)
 114 {
 115         int rc;
 116 
 117         pr_devel("CXL interrupt: Segment fault pe: %i ea: %#llx\n", ctx->pe, ea);
 118         trace_cxl_ste_miss(ctx, ea);
 119 
 120         if ((rc = cxl_fault_segment(ctx, mm, ea)))
 121                 cxl_ack_ae(ctx);
 122         else {
 123 
 124                 mb(); /* Order seg table write to TFC MMIO write */
 125                 cxl_ops->ack_irq(ctx, CXL_PSL_TFC_An_R, 0);
 126         }
 127 
 128         return IRQ_HANDLED;
 129 }
 130 
 131 int cxl_handle_mm_fault(struct mm_struct *mm, u64 dsisr, u64 dar)
 132 {
 133         vm_fault_t flt = 0;
 134         int result;
 135         unsigned long access, flags, inv_flags = 0;
 136 
 137         /*
 138          * Add the fault handling cpu to task mm cpumask so that we
 139          * can do a safe lockless page table walk when inserting the
 140          * hash page table entry. This function get called with a
 141          * valid mm for user space addresses. Hence using the if (mm)
 142          * check is sufficient here.
 143          */
 144         if (mm && !cpumask_test_cpu(smp_processor_id(), mm_cpumask(mm))) {
 145                 cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
 146                 /*
 147                  * We need to make sure we walk the table only after
 148                  * we update the cpumask. The other side of the barrier
 149                  * is explained in serialize_against_pte_lookup()
 150                  */
 151                 smp_mb();
 152         }
 153         if ((result = copro_handle_mm_fault(mm, dar, dsisr, &flt))) {
 154                 pr_devel("copro_handle_mm_fault failed: %#x\n", result);
 155                 return result;
 156         }
 157 
 158         if (!radix_enabled()) {
 159                 /*
 160                  * update_mmu_cache() will not have loaded the hash since current->trap
 161                  * is not a 0x400 or 0x300, so just call hash_page_mm() here.
 162                  */
 163                 access = _PAGE_PRESENT | _PAGE_READ;
 164                 if (dsisr & CXL_PSL_DSISR_An_S)
 165                         access |= _PAGE_WRITE;
 166 
 167                 if (!mm && (get_region_id(dar) != USER_REGION_ID))
 168                         access |= _PAGE_PRIVILEGED;
 169 
 170                 if (dsisr & DSISR_NOHPTE)
 171                         inv_flags |= HPTE_NOHPTE_UPDATE;
 172 
 173                 local_irq_save(flags);
 174                 hash_page_mm(mm, dar, access, 0x300, inv_flags);
 175                 local_irq_restore(flags);
 176         }
 177         return 0;
 178 }
 179 
 180 static void cxl_handle_page_fault(struct cxl_context *ctx,
 181                                   struct mm_struct *mm,
 182                                   u64 dsisr, u64 dar)
 183 {
 184         trace_cxl_pte_miss(ctx, dsisr, dar);
 185 
 186         if (cxl_handle_mm_fault(mm, dsisr, dar)) {
 187                 cxl_ack_ae(ctx);
 188         } else {
 189                 pr_devel("Page fault successfully handled for pe: %i!\n", ctx->pe);
 190                 cxl_ops->ack_irq(ctx, CXL_PSL_TFC_An_R, 0);
 191         }
 192 }
 193 
 194 /*
 195  * Returns the mm_struct corresponding to the context ctx.
 196  * mm_users == 0, the context may be in the process of being closed.
 197  */
 198 static struct mm_struct *get_mem_context(struct cxl_context *ctx)
 199 {
 200         if (ctx->mm == NULL)
 201                 return NULL;
 202 
 203         if (!atomic_inc_not_zero(&ctx->mm->mm_users))
 204                 return NULL;
 205 
 206         return ctx->mm;
 207 }
 208 
 209 static bool cxl_is_segment_miss(struct cxl_context *ctx, u64 dsisr)
 210 {
 211         if ((cxl_is_power8() && (dsisr & CXL_PSL_DSISR_An_DS)))
 212                 return true;
 213 
 214         return false;
 215 }
 216 
 217 static bool cxl_is_page_fault(struct cxl_context *ctx, u64 dsisr)
 218 {
 219         if ((cxl_is_power8()) && (dsisr & CXL_PSL_DSISR_An_DM))
 220                 return true;
 221 
 222         if (cxl_is_power9())
 223                 return true;
 224 
 225         return false;
 226 }
 227 
 228 void cxl_handle_fault(struct work_struct *fault_work)
 229 {
 230         struct cxl_context *ctx =
 231                 container_of(fault_work, struct cxl_context, fault_work);
 232         u64 dsisr = ctx->dsisr;
 233         u64 dar = ctx->dar;
 234         struct mm_struct *mm = NULL;
 235 
 236         if (cpu_has_feature(CPU_FTR_HVMODE)) {
 237                 if (cxl_p2n_read(ctx->afu, CXL_PSL_DSISR_An) != dsisr ||
 238                     cxl_p2n_read(ctx->afu, CXL_PSL_DAR_An) != dar ||
 239                     cxl_p2n_read(ctx->afu, CXL_PSL_PEHandle_An) != ctx->pe) {
 240                         /* Most likely explanation is harmless - a dedicated
 241                          * process has detached and these were cleared by the
 242                          * PSL purge, but warn about it just in case
 243                          */
 244                         dev_notice(&ctx->afu->dev, "cxl_handle_fault: Translation fault regs changed\n");
 245                         return;
 246                 }
 247         }
 248 
 249         /* Early return if the context is being / has been detached */
 250         if (ctx->status == CLOSED) {
 251                 cxl_ack_ae(ctx);
 252                 return;
 253         }
 254 
 255         pr_devel("CXL BOTTOM HALF handling fault for afu pe: %i. "
 256                 "DSISR: %#llx DAR: %#llx\n", ctx->pe, dsisr, dar);
 257 
 258         if (!ctx->kernel) {
 259 
 260                 mm = get_mem_context(ctx);
 261                 if (mm == NULL) {
 262                         pr_devel("%s: unable to get mm for pe=%d pid=%i\n",
 263                                  __func__, ctx->pe, pid_nr(ctx->pid));
 264                         cxl_ack_ae(ctx);
 265                         return;
 266                 } else {
 267                         pr_devel("Handling page fault for pe=%d pid=%i\n",
 268                                  ctx->pe, pid_nr(ctx->pid));
 269                 }
 270         }
 271 
 272         if (cxl_is_segment_miss(ctx, dsisr))
 273                 cxl_handle_segment_miss(ctx, mm, dar);
 274         else if (cxl_is_page_fault(ctx, dsisr))
 275                 cxl_handle_page_fault(ctx, mm, dsisr, dar);
 276         else
 277                 WARN(1, "cxl_handle_fault has nothing to handle\n");
 278 
 279         if (mm)
 280                 mmput(mm);
 281 }
 282 
 283 static void cxl_prefault_one(struct cxl_context *ctx, u64 ea)
 284 {
 285         struct mm_struct *mm;
 286 
 287         mm = get_mem_context(ctx);
 288         if (mm == NULL) {
 289                 pr_devel("cxl_prefault_one unable to get mm %i\n",
 290                          pid_nr(ctx->pid));
 291                 return;
 292         }
 293 
 294         cxl_fault_segment(ctx, mm, ea);
 295 
 296         mmput(mm);
 297 }
 298 
 299 static u64 next_segment(u64 ea, u64 vsid)
 300 {
 301         if (vsid & SLB_VSID_B_1T)
 302                 ea |= (1ULL << 40) - 1;
 303         else
 304                 ea |= (1ULL << 28) - 1;
 305 
 306         return ea + 1;
 307 }
 308 
 309 static void cxl_prefault_vma(struct cxl_context *ctx)
 310 {
 311         u64 ea, last_esid = 0;
 312         struct copro_slb slb;
 313         struct vm_area_struct *vma;
 314         int rc;
 315         struct mm_struct *mm;
 316 
 317         mm = get_mem_context(ctx);
 318         if (mm == NULL) {
 319                 pr_devel("cxl_prefault_vm unable to get mm %i\n",
 320                          pid_nr(ctx->pid));
 321                 return;
 322         }
 323 
 324         down_read(&mm->mmap_sem);
 325         for (vma = mm->mmap; vma; vma = vma->vm_next) {
 326                 for (ea = vma->vm_start; ea < vma->vm_end;
 327                                 ea = next_segment(ea, slb.vsid)) {
 328                         rc = copro_calculate_slb(mm, ea, &slb);
 329                         if (rc)
 330                                 continue;
 331 
 332                         if (last_esid == slb.esid)
 333                                 continue;
 334 
 335                         cxl_load_segment(ctx, &slb);
 336                         last_esid = slb.esid;
 337                 }
 338         }
 339         up_read(&mm->mmap_sem);
 340 
 341         mmput(mm);
 342 }
 343 
 344 void cxl_prefault(struct cxl_context *ctx, u64 wed)
 345 {
 346         switch (ctx->afu->prefault_mode) {
 347         case CXL_PREFAULT_WED:
 348                 cxl_prefault_one(ctx, wed);
 349                 break;
 350         case CXL_PREFAULT_ALL:
 351                 cxl_prefault_vma(ctx);
 352                 break;
 353         default:
 354                 break;
 355         }
 356 }