drivers/iommu/intel-svm.c

   1 /*
   2  * Copyright © 2015 Intel Corporation.
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms and conditions of the GNU General Public License,
   6  * version 2, as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  11  * more details.
  12  *
  13  * Authors: David Woodhouse <dwmw2@infradead.org>
  14  */
  15
  16 #include <linux/intel-iommu.h>
  17 #include <linux/mmu_notifier.h>
  18 #include <linux/sched.h>
  19 #include <linux/slab.h>
  20 #include <linux/intel-svm.h>
  21 #include <linux/rculist.h>
  22 #include <linux/pci.h>
  23 #include <linux/pci-ats.h>
  24 #include <linux/dmar.h>
  25 #include <linux/interrupt.h>
  26
  27 static irqreturn_t prq_event_thread(int irq, void *d);
  28
  29 struct pasid_entry {
  30         u64 val;
  31 };
  32
  33 struct pasid_state_entry {
  34         u64 val;
  35 };
  36
  37 int intel_svm_alloc_pasid_tables(struct intel_iommu *iommu)
  38 {
  39         struct page *pages;
  40         int order;
  41
  42         order = ecap_pss(iommu->ecap) + 7 - PAGE_SHIFT;
  43         if (order < 0)
  44                 order = 0;
  45
  46         pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, order);
  47         if (!pages) {
  48                 pr_warn("IOMMU: %s: Failed to allocate PASID table\n",
  49                         iommu->name);
  50                 return -ENOMEM;
  51         }
  52         iommu->pasid_table = page_address(pages);
  53         pr_info("%s: Allocated order %d PASID table.\n", iommu->name, order);
  54
  55         if (ecap_dis(iommu->ecap)) {
  56                 pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, order);
  57                 if (pages)
  58                         iommu->pasid_state_table = page_address(pages);
  59                 else
  60                         pr_warn("IOMMU: %s: Failed to allocate PASID state table\n",
  61                                 iommu->name);
  62         }
  63
  64         idr_init(&iommu->pasid_idr);
  65
  66         return 0;
  67 }
  68
  69 int intel_svm_free_pasid_tables(struct intel_iommu *iommu)
  70 {
  71         int order;
  72
  73         order = ecap_pss(iommu->ecap) + 7 - PAGE_SHIFT;
  74         if (order < 0)
  75                 order = 0;
  76
  77         if (iommu->pasid_table) {
  78                 free_pages((unsigned long)iommu->pasid_table, order);
  79                 iommu->pasid_table = NULL;
  80         }
  81         if (iommu->pasid_state_table) {
  82                 free_pages((unsigned long)iommu->pasid_state_table, order);
  83                 iommu->pasid_state_table = NULL;
  84         }
  85         idr_destroy(&iommu->pasid_idr);
  86         return 0;
  87 }
  88
  89 #define PRQ_ORDER 0
  90
  91 int intel_svm_enable_prq(struct intel_iommu *iommu)
  92 {
  93         struct page *pages;
  94         int irq, ret;
  95
  96         pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, PRQ_ORDER);
  97         if (!pages) {
  98                 pr_warn("IOMMU: %s: Failed to allocate page request queue\n",
  99                         iommu->name);
 100                 return -ENOMEM;
 101         }
 102         iommu->prq = page_address(pages);
 103
 104         irq = dmar_alloc_hwirq(DMAR_UNITS_SUPPORTED + iommu->seq_id, iommu->node, iommu);
 105         if (irq <= 0) {
 106                 pr_err("IOMMU: %s: Failed to create IRQ vector for page request queue\n",
 107                        iommu->name);
 108                 ret = -EINVAL;
 109         err:
 110                 free_pages((unsigned long)iommu->prq, PRQ_ORDER);
 111                 iommu->prq = NULL;
 112                 return ret;
 113         }
 114         iommu->pr_irq = irq;
 115
 116         snprintf(iommu->prq_name, sizeof(iommu->prq_name), "dmar%d-prq", iommu->seq_id);
 117
 118         ret = request_threaded_irq(irq, NULL, prq_event_thread, IRQF_ONESHOT,
 119                                    iommu->prq_name, iommu);
 120         if (ret) {
 121                 pr_err("IOMMU: %s: Failed to request IRQ for page request queue\n",
 122                        iommu->name);
 123                 dmar_free_hwirq(irq);
 124                 goto err;
 125         }
 126         dmar_writeq(iommu->reg + DMAR_PQH_REG, 0ULL);
 127         dmar_writeq(iommu->reg + DMAR_PQT_REG, 0ULL);
 128         dmar_writeq(iommu->reg + DMAR_PQA_REG, virt_to_phys(iommu->prq) | PRQ_ORDER);
 129
 130         return 0;
 131 }
 132
 133 int intel_svm_finish_prq(struct intel_iommu *iommu)
 134 {
 135         dmar_writeq(iommu->reg + DMAR_PQH_REG, 0ULL);
 136         dmar_writeq(iommu->reg + DMAR_PQT_REG, 0ULL);
 137         dmar_writeq(iommu->reg + DMAR_PQA_REG, 0ULL);
 138
 139         free_irq(iommu->pr_irq, iommu);
 140         dmar_free_hwirq(iommu->pr_irq);
 141         iommu->pr_irq = 0;
 142
 143         free_pages((unsigned long)iommu->prq, PRQ_ORDER);
 144         iommu->prq = NULL;
 145
 146         return 0;
 147 }
 148
 149 static void intel_flush_svm_range_dev (struct intel_svm *svm, struct intel_svm_dev *sdev,
 150                                        unsigned long address, unsigned long pages, int ih, int gl)
 151 {
 152         struct qi_desc desc;
 153
 154         if (pages == -1) {
 155                 /* For global kernel pages we have to flush them in *all* PASIDs
 156                  * because that's the only option the hardware gives us. Despite
 157                  * the fact that they are actually only accessible through one. */
 158                 if (gl)
 159                         desc.low = QI_EIOTLB_PASID(svm->pasid) | QI_EIOTLB_DID(sdev->did) |
 160                                 QI_EIOTLB_GRAN(QI_GRAN_ALL_ALL) | QI_EIOTLB_TYPE;
 161                 else
 162                         desc.low = QI_EIOTLB_PASID(svm->pasid) | QI_EIOTLB_DID(sdev->did) |
 163                                 QI_EIOTLB_GRAN(QI_GRAN_NONG_PASID) | QI_EIOTLB_TYPE;
 164                 desc.high = 0;
 165         } else {
 166                 int mask = ilog2(__roundup_pow_of_two(pages));
 167
 168                 desc.low = QI_EIOTLB_PASID(svm->pasid) | QI_EIOTLB_DID(sdev->did) |
 169                         QI_EIOTLB_GRAN(QI_GRAN_PSI_PASID) | QI_EIOTLB_TYPE;
 170                 desc.high = QI_EIOTLB_ADDR(address) | QI_EIOTLB_GL(gl) |
 171                         QI_EIOTLB_IH(ih) | QI_EIOTLB_AM(mask);
 172         }
 173         qi_submit_sync(&desc, svm->iommu);
 174
 175         if (sdev->dev_iotlb) {
 176                 desc.low = QI_DEV_EIOTLB_PASID(svm->pasid) | QI_DEV_EIOTLB_SID(sdev->sid) |
 177                         QI_DEV_EIOTLB_QDEP(sdev->qdep) | QI_DEIOTLB_TYPE;
 178                 if (pages == -1) {
 179                         desc.high = QI_DEV_EIOTLB_ADDR(-1ULL >> 1) | QI_DEV_EIOTLB_SIZE;
 180                 } else if (pages > 1) {
 181                         /* The least significant zero bit indicates the size. So,
 182                          * for example, an "address" value of 0x12345f000 will
 183                          * flush from 0x123440000 to 0x12347ffff (256KiB). */
 184                         unsigned long last = address + ((unsigned long)(pages - 1) << VTD_PAGE_SHIFT);
 185                         unsigned long mask = __rounddown_pow_of_two(address ^ last);;
 186
 187                         desc.high = QI_DEV_EIOTLB_ADDR((address & ~mask) | (mask - 1)) | QI_DEV_EIOTLB_SIZE;
 188                 } else {
 189                         desc.high = QI_DEV_EIOTLB_ADDR(address);
 190                 }
 191                 qi_submit_sync(&desc, svm->iommu);
 192         }
 193 }
 194
 195 static void intel_flush_svm_range(struct intel_svm *svm, unsigned long address,
 196                                   unsigned long pages, int ih, int gl)
 197 {
 198         struct intel_svm_dev *sdev;
 199
 200         /* Try deferred invalidate if available */
 201         if (svm->iommu->pasid_state_table &&
 202             !cmpxchg64(&svm->iommu->pasid_state_table[svm->pasid].val, 0, 1ULL << 63))
 203                 return;
 204
 205         rcu_read_lock();
 206         list_for_each_entry_rcu(sdev, &svm->devs, list)
 207                 intel_flush_svm_range_dev(svm, sdev, address, pages, ih, gl);
 208         rcu_read_unlock();
 209 }
 210
 211 static void intel_change_pte(struct mmu_notifier *mn, struct mm_struct *mm,
 212                              unsigned long address, pte_t pte)
 213 {
 214         struct intel_svm *svm = container_of(mn, struct intel_svm, notifier);
 215
 216         intel_flush_svm_range(svm, address, 1, 1, 0);
 217 }
 218
 219 static void intel_invalidate_page(struct mmu_notifier *mn, struct mm_struct *mm,
 220                                   unsigned long address)
 221 {
 222         struct intel_svm *svm = container_of(mn, struct intel_svm, notifier);
 223
 224         intel_flush_svm_range(svm, address, 1, 1, 0);
 225 }
 226
 227 /* Pages have been freed at this point */
 228 static void intel_invalidate_range(struct mmu_notifier *mn,
 229                                    struct mm_struct *mm,
 230                                    unsigned long start, unsigned long end)
 231 {
 232         struct intel_svm *svm = container_of(mn, struct intel_svm, notifier);
 233
 234         intel_flush_svm_range(svm, start,
 235                               (end - start + PAGE_SIZE - 1) >> VTD_PAGE_SHIFT, 0, 0);
 236 }
 237
 238
 239 static void intel_flush_pasid_dev(struct intel_svm *svm, struct intel_svm_dev *sdev, int pasid)
 240 {
 241         struct qi_desc desc;
 242
 243         desc.high = 0;
 244         desc.low = QI_PC_TYPE | QI_PC_DID(sdev->did) | QI_PC_PASID_SEL | QI_PC_PASID(pasid);
 245
 246         qi_submit_sync(&desc, svm->iommu);
 247 }
 248
 249 static void intel_mm_release(struct mmu_notifier *mn, struct mm_struct *mm)
 250 {
 251         struct intel_svm *svm = container_of(mn, struct intel_svm, notifier);
 252         struct intel_svm_dev *sdev;
 253
 254         /* This might end up being called from exit_mmap(), *before* the page
 255          * tables are cleared. And __mmu_notifier_release() will delete us from
 256          * the list of notifiers so that our invalidate_range() callback doesn't
 257          * get called when the page tables are cleared. So we need to protect
 258          * against hardware accessing those page tables.
 259          *
 260          * We do it by clearing the entry in the PASID table and then flushing
 261          * the IOTLB and the PASID table caches. This might upset hardware;
 262          * perhaps we'll want to point the PASID to a dummy PGD (like the zero
 263          * page) so that we end up taking a fault that the hardware really
 264          * *has* to handle gracefully without affecting other processes.
 265          */
 266         svm->iommu->pasid_table[svm->pasid].val = 0;
 267         wmb();
 268
 269         rcu_read_lock();
 270         list_for_each_entry_rcu(sdev, &svm->devs, list) {
 271                 intel_flush_pasid_dev(svm, sdev, svm->pasid);
 272                 intel_flush_svm_range_dev(svm, sdev, 0, -1, 0, !svm->mm);
 273         }
 274         rcu_read_unlock();
 275
 276 }
 277
 278 static const struct mmu_notifier_ops intel_mmuops = {
 279         .release = intel_mm_release,
 280         .change_pte = intel_change_pte,
 281         .invalidate_page = intel_invalidate_page,
 282         .invalidate_range = intel_invalidate_range,
 283 };
 284
 285 static DEFINE_MUTEX(pasid_mutex);
 286
 287 int intel_svm_bind_mm(struct device *dev, int *pasid, int flags, struct svm_dev_ops *ops)
 288 {
 289         struct intel_iommu *iommu = intel_svm_device_to_iommu(dev);
 290         struct intel_svm_dev *sdev;
 291         struct intel_svm *svm = NULL;
 292         struct mm_struct *mm = NULL;
 293         int pasid_max;
 294         int ret;
 295
 296         if (WARN_ON(!iommu))
 297                 return -EINVAL;
 298
 299         if (dev_is_pci(dev)) {
 300                 pasid_max = pci_max_pasids(to_pci_dev(dev));
 301                 if (pasid_max < 0)
 302                         return -EINVAL;
 303         } else
 304                 pasid_max = 1 << 20;
 305
 306         if ((flags & SVM_FLAG_SUPERVISOR_MODE)) {
 307                 if (!ecap_srs(iommu->ecap))
 308                         return -EINVAL;
 309         } else if (pasid) {
 310                 mm = get_task_mm(current);
 311                 BUG_ON(!mm);
 312         }
 313
 314         mutex_lock(&pasid_mutex);
 315         if (pasid && !(flags & SVM_FLAG_PRIVATE_PASID)) {
 316                 int i;
 317
 318                 idr_for_each_entry(&iommu->pasid_idr, svm, i) {
 319                         if (svm->mm != mm ||
 320                             (svm->flags & SVM_FLAG_PRIVATE_PASID))
 321                                 continue;
 322
 323                         if (svm->pasid >= pasid_max) {
 324                                 dev_warn(dev,
 325                                          "Limited PASID width. Cannot use existing PASID %d\n",
 326                                          svm->pasid);
 327                                 ret = -ENOSPC;
 328                                 goto out;
 329                         }
 330
 331                         list_for_each_entry(sdev, &svm->devs, list) {
 332                                 if (dev == sdev->dev) {
 333                                         if (sdev->ops != ops) {
 334                                                 ret = -EBUSY;
 335                                                 goto out;
 336                                         }
 337                                         sdev->users++;
 338                                         goto success;
 339                                 }
 340                         }
 341
 342                         break;
 343                 }
 344         }
 345
 346         sdev = kzalloc(sizeof(*sdev), GFP_KERNEL);
 347         if (!sdev) {
 348                 ret = -ENOMEM;
 349                 goto out;
 350         }
 351         sdev->dev = dev;
 352
 353         ret = intel_iommu_enable_pasid(iommu, sdev);
 354         if (ret || !pasid) {
 355                 /* If they don't actually want to assign a PASID, this is
 356                  * just an enabling check/preparation. */
 357                 kfree(sdev);
 358                 goto out;
 359         }
 360         /* Finish the setup now we know we're keeping it */
 361         sdev->users = 1;
 362         sdev->ops = ops;
 363         init_rcu_head(&sdev->rcu);
 364
 365         if (!svm) {
 366                 svm = kzalloc(sizeof(*svm), GFP_KERNEL);
 367                 if (!svm) {
 368                         ret = -ENOMEM;
 369                         kfree(sdev);
 370                         goto out;
 371                 }
 372                 svm->iommu = iommu;
 373
 374                 if (pasid_max > 2 << ecap_pss(iommu->ecap))
 375                         pasid_max = 2 << ecap_pss(iommu->ecap);
 376
 377                 /* Do not use PASID 0 in caching mode (virtualised IOMMU) */
 378                 ret = idr_alloc(&iommu->pasid_idr, svm,
 379                                 !!cap_caching_mode(iommu->cap),
 380                                 pasid_max - 1, GFP_KERNEL);
 381                 if (ret < 0) {
 382                         kfree(svm);
 383                         goto out;
 384                 }
 385                 svm->pasid = ret;
 386                 svm->notifier.ops = &intel_mmuops;
 387                 svm->mm = mm;
 388                 svm->flags = flags;
 389                 INIT_LIST_HEAD_RCU(&svm->devs);
 390                 ret = -ENOMEM;
 391                 if (mm) {
 392                         ret = mmu_notifier_register(&svm->notifier, mm);
 393                         if (ret) {
 394                                 idr_remove(&svm->iommu->pasid_idr, svm->pasid);
 395                                 kfree(svm);
 396                                 kfree(sdev);
 397                                 goto out;
 398                         }
 399                         iommu->pasid_table[svm->pasid].val = (u64)__pa(mm->pgd) | 1;
 400                 } else
 401                         iommu->pasid_table[svm->pasid].val = (u64)__pa(init_mm.pgd) | 1 | (1ULL << 11);
 402                 wmb();
 403                 /* In caching mode, we still have to flush with PASID 0 when
 404                  * a PASID table entry becomes present. Not entirely clear
 405                  * *why* that would be the case — surely we could just issue
 406                  * a flush with the PASID value that we've changed? The PASID
 407                  * is the index into the table, after all. It's not like domain
 408                  * IDs in the case of the equivalent context-entry change in
 409                  * caching mode. And for that matter it's not entirely clear why
 410                  * a VMM would be in the business of caching the PASID table
 411                  * anyway. Surely that can be left entirely to the guest? */
 412                 if (cap_caching_mode(iommu->cap))
 413                         intel_flush_pasid_dev(svm, sdev, 0);
 414         }
 415         list_add_rcu(&sdev->list, &svm->devs);
 416
 417  success:
 418         *pasid = svm->pasid;
 419         ret = 0;
 420  out:
 421         mutex_unlock(&pasid_mutex);
 422         if (mm)
 423                 mmput(mm);
 424         return ret;
 425 }
 426 EXPORT_SYMBOL_GPL(intel_svm_bind_mm);
 427
 428 int intel_svm_unbind_mm(struct device *dev, int pasid)
 429 {
 430         struct intel_svm_dev *sdev;
 431         struct intel_iommu *iommu;
 432         struct intel_svm *svm;
 433         int ret = -EINVAL;
 434
 435         mutex_lock(&pasid_mutex);
 436         iommu = intel_svm_device_to_iommu(dev);
 437         if (!iommu || !iommu->pasid_table)
 438                 goto out;
 439
 440         svm = idr_find(&iommu->pasid_idr, pasid);
 441         if (!svm)
 442                 goto out;
 443
 444         list_for_each_entry(sdev, &svm->devs, list) {
 445                 if (dev == sdev->dev) {
 446                         ret = 0;
 447                         sdev->users--;
 448                         if (!sdev->users) {
 449                                 list_del_rcu(&sdev->list);
 450                                 /* Flush the PASID cache and IOTLB for this device.
 451                                  * Note that we do depend on the hardware *not* using
 452                                  * the PASID any more. Just as we depend on other
 453                                  * devices never using PASIDs that they have no right
 454                                  * to use. We have a *shared* PASID table, because it's
 455                                  * large and has to be physically contiguous. So it's
 456                                  * hard to be as defensive as we might like. */
 457                                 intel_flush_pasid_dev(svm, sdev, svm->pasid);
 458                                 intel_flush_svm_range_dev(svm, sdev, 0, -1, 0, !svm->mm);
 459                                 kfree_rcu(sdev, rcu);
 460
 461                                 if (list_empty(&svm->devs)) {
 462
 463                                         idr_remove(&svm->iommu->pasid_idr, svm->pasid);
 464                                         if (svm->mm)
 465                                                 mmu_notifier_unregister(&svm->notifier, svm->mm);
 466
 467                                         /* We mandate that no page faults may be outstanding
 468                                          * for the PASID when intel_svm_unbind_mm() is called.
 469                                          * If that is not obeyed, subtle errors will happen.
 470                                          * Let's make them less subtle... */
 471                                         memset(svm, 0x6b, sizeof(*svm));
 472                                         kfree(svm);
 473                                 }
 474                         }
 475                         break;
 476                 }
 477         }
 478  out:
 479         mutex_unlock(&pasid_mutex);
 480
 481         return ret;
 482 }
 483 EXPORT_SYMBOL_GPL(intel_svm_unbind_mm);
 484
 485 /* Page request queue descriptor */
 486 struct page_req_dsc {
 487         u64 srr:1;
 488         u64 bof:1;
 489         u64 pasid_present:1;
 490         u64 lpig:1;
 491         u64 pasid:20;
 492         u64 bus:8;
 493         u64 private:23;
 494         u64 prg_index:9;
 495         u64 rd_req:1;
 496         u64 wr_req:1;
 497         u64 exe_req:1;
 498         u64 priv_req:1;
 499         u64 devfn:8;
 500         u64 addr:52;
 501 };
 502
 503 #define PRQ_RING_MASK ((0x1000 << PRQ_ORDER) - 0x10)
 504
 505 static bool access_error(struct vm_area_struct *vma, struct page_req_dsc *req)
 506 {
 507         unsigned long requested = 0;
 508
 509         if (req->exe_req)
 510                 requested |= VM_EXEC;
 511
 512         if (req->rd_req)
 513                 requested |= VM_READ;
 514
 515         if (req->wr_req)
 516                 requested |= VM_WRITE;
 517
 518         return (requested & ~vma->vm_flags) != 0;
 519 }
 520
 521 static irqreturn_t prq_event_thread(int irq, void *d)
 522 {
 523         struct intel_iommu *iommu = d;
 524         struct intel_svm *svm = NULL;
 525         int head, tail, handled = 0;
 526
 527         /* Clear PPR bit before reading head/tail registers, to
 528          * ensure that we get a new interrupt if needed. */
 529         writel(DMA_PRS_PPR, iommu->reg + DMAR_PRS_REG);
 530
 531         tail = dmar_readq(iommu->reg + DMAR_PQT_REG) & PRQ_RING_MASK;
 532         head = dmar_readq(iommu->reg + DMAR_PQH_REG) & PRQ_RING_MASK;
 533         while (head != tail) {
 534                 struct intel_svm_dev *sdev;
 535                 struct vm_area_struct *vma;
 536                 struct page_req_dsc *req;
 537                 struct qi_desc resp;
 538                 int ret, result;
 539                 u64 address;
 540
 541                 handled = 1;
 542
 543                 req = &iommu->prq[head / sizeof(*req)];
 544
 545                 result = QI_RESP_FAILURE;
 546                 address = (u64)req->addr << VTD_PAGE_SHIFT;
 547                 if (!req->pasid_present) {
 548                         pr_err("%s: Page request without PASID: %08llx %08llx\n",
 549                                iommu->name, ((unsigned long long *)req)[0],
 550                                ((unsigned long long *)req)[1]);
 551                         goto bad_req;
 552                 }
 553
 554                 if (!svm || svm->pasid != req->pasid) {
 555                         rcu_read_lock();
 556                         svm = idr_find(&iommu->pasid_idr, req->pasid);
 557                         /* It *can't* go away, because the driver is not permitted
 558                          * to unbind the mm while any page faults are outstanding.
 559                          * So we only need RCU to protect the internal idr code. */
 560                         rcu_read_unlock();
 561
 562                         if (!svm) {
 563                                 pr_err("%s: Page request for invalid PASID %d: %08llx %08llx\n",
 564                                        iommu->name, req->pasid, ((unsigned long long *)req)[0],
 565                                        ((unsigned long long *)req)[1]);
 566                                 goto no_pasid;
 567                         }
 568                 }
 569
 570                 result = QI_RESP_INVALID;
 571                 /* Since we're using init_mm.pgd directly, we should never take
 572                  * any faults on kernel addresses. */
 573                 if (!svm->mm)
 574                         goto bad_req;
 575                 /* If the mm is already defunct, don't handle faults. */
 576                 if (!atomic_inc_not_zero(&svm->mm->mm_users))
 577                         goto bad_req;
 578                 down_read(&svm->mm->mmap_sem);
 579                 vma = find_extend_vma(svm->mm, address);
 580                 if (!vma || address < vma->vm_start)
 581                         goto invalid;
 582
 583                 if (access_error(vma, req))
 584                         goto invalid;
 585
 586                 ret = handle_mm_fault(vma, address,
 587                                       req->wr_req ? FAULT_FLAG_WRITE : 0);
 588                 if (ret & VM_FAULT_ERROR)
 589                         goto invalid;
 590
 591                 result = QI_RESP_SUCCESS;
 592         invalid:
 593                 up_read(&svm->mm->mmap_sem);
 594                 mmput(svm->mm);
 595         bad_req:
 596                 /* Accounting for major/minor faults? */
 597                 rcu_read_lock();
 598                 list_for_each_entry_rcu(sdev, &svm->devs, list) {
 599                         if (sdev->sid == PCI_DEVID(req->bus, req->devfn))
 600                                 break;
 601                 }
 602                 /* Other devices can go away, but the drivers are not permitted
 603                  * to unbind while any page faults might be in flight. So it's
 604                  * OK to drop the 'lock' here now we have it. */
 605                 rcu_read_unlock();
 606
 607                 if (WARN_ON(&sdev->list == &svm->devs))
 608                         sdev = NULL;
 609
 610                 if (sdev && sdev->ops && sdev->ops->fault_cb) {
 611                         int rwxp = (req->rd_req << 3) | (req->wr_req << 2) |
 612                                 (req->exe_req << 1) | (req->priv_req);
 613                         sdev->ops->fault_cb(sdev->dev, req->pasid, req->addr, req->private, rwxp, result);
 614                 }
 615                 /* We get here in the error case where the PASID lookup failed,
 616                    and these can be NULL. Do not use them below this point! */
 617                 sdev = NULL;
 618                 svm = NULL;
 619         no_pasid:
 620                 if (req->lpig) {
 621                         /* Page Group Response */
 622                         resp.low = QI_PGRP_PASID(req->pasid) |
 623                                 QI_PGRP_DID((req->bus << 8) | req->devfn) |
 624                                 QI_PGRP_PASID_P(req->pasid_present) |
 625                                 QI_PGRP_RESP_TYPE;
 626                         resp.high = QI_PGRP_IDX(req->prg_index) |
 627                                 QI_PGRP_PRIV(req->private) | QI_PGRP_RESP_CODE(result);
 628
 629                         qi_submit_sync(&resp, iommu);
 630                 } else if (req->srr) {
 631                         /* Page Stream Response */
 632                         resp.low = QI_PSTRM_IDX(req->prg_index) |
 633                                 QI_PSTRM_PRIV(req->private) | QI_PSTRM_BUS(req->bus) |
 634                                 QI_PSTRM_PASID(req->pasid) | QI_PSTRM_RESP_TYPE;
 635                         resp.high = QI_PSTRM_ADDR(address) | QI_PSTRM_DEVFN(req->devfn) |
 636                                 QI_PSTRM_RESP_CODE(result);
 637
 638                         qi_submit_sync(&resp, iommu);
 639                 }
 640
 641                 head = (head + sizeof(*req)) & PRQ_RING_MASK;
 642         }
 643
 644         dmar_writeq(iommu->reg + DMAR_PQH_REG, tail);
 645
 646         return IRQ_RETVAL(handled);
 647 }