root/drivers/iommu/intel-svm.c

DEFINITIONS

1. intel_svm_init
2. intel_svm_enable_prq
3. intel_svm_finish_prq
4. intel_flush_svm_range_dev
5. intel_flush_svm_range
6. intel_invalidate_range
7. intel_mm_release
8. intel_svm_bind_mm
9. intel_svm_unbind_mm
10. intel_svm_is_pasid_valid
11. access_error
12. is_canonical_address
13. prq_event_thread

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright © 2015 Intel Corporation.
   4  *
   5  * Authors: David Woodhouse <dwmw2@infradead.org>
   6  */
   7 
   8 #include <linux/intel-iommu.h>
   9 #include <linux/mmu_notifier.h>
  10 #include <linux/sched.h>
  11 #include <linux/sched/mm.h>
  12 #include <linux/slab.h>
  13 #include <linux/intel-svm.h>
  14 #include <linux/rculist.h>
  15 #include <linux/pci.h>
  16 #include <linux/pci-ats.h>
  17 #include <linux/dmar.h>
  18 #include <linux/interrupt.h>
  19 #include <linux/mm_types.h>
  20 #include <asm/page.h>
  21 
  22 #include "intel-pasid.h"
  23 
  24 static irqreturn_t prq_event_thread(int irq, void *d);
  25 
  26 int intel_svm_init(struct intel_iommu *iommu)
  27 {
  28         if (cpu_feature_enabled(X86_FEATURE_GBPAGES) &&
  29                         !cap_fl1gp_support(iommu->cap))
  30                 return -EINVAL;
  31 
  32         if (cpu_feature_enabled(X86_FEATURE_LA57) &&
  33                         !cap_5lp_support(iommu->cap))
  34                 return -EINVAL;
  35 
  36         return 0;
  37 }
  38 
  39 #define PRQ_ORDER 0
  40 
  41 int intel_svm_enable_prq(struct intel_iommu *iommu)
  42 {
  43         struct page *pages;
  44         int irq, ret;
  45 
  46         pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, PRQ_ORDER);
  47         if (!pages) {
  48                 pr_warn("IOMMU: %s: Failed to allocate page request queue\n",
  49                         iommu->name);
  50                 return -ENOMEM;
  51         }
  52         iommu->prq = page_address(pages);
  53 
  54         irq = dmar_alloc_hwirq(DMAR_UNITS_SUPPORTED + iommu->seq_id, iommu->node, iommu);
  55         if (irq <= 0) {
  56                 pr_err("IOMMU: %s: Failed to create IRQ vector for page request queue\n",
  57                        iommu->name);
  58                 ret = -EINVAL;
  59         err:
  60                 free_pages((unsigned long)iommu->prq, PRQ_ORDER);
  61                 iommu->prq = NULL;
  62                 return ret;
  63         }
  64         iommu->pr_irq = irq;
  65 
  66         snprintf(iommu->prq_name, sizeof(iommu->prq_name), "dmar%d-prq", iommu->seq_id);
  67 
  68         ret = request_threaded_irq(irq, NULL, prq_event_thread, IRQF_ONESHOT,
  69                                    iommu->prq_name, iommu);
  70         if (ret) {
  71                 pr_err("IOMMU: %s: Failed to request IRQ for page request queue\n",
  72                        iommu->name);
  73                 dmar_free_hwirq(irq);
  74                 iommu->pr_irq = 0;
  75                 goto err;
  76         }
  77         dmar_writeq(iommu->reg + DMAR_PQH_REG, 0ULL);
  78         dmar_writeq(iommu->reg + DMAR_PQT_REG, 0ULL);
  79         dmar_writeq(iommu->reg + DMAR_PQA_REG, virt_to_phys(iommu->prq) | PRQ_ORDER);
  80 
  81         return 0;
  82 }
  83 
  84 int intel_svm_finish_prq(struct intel_iommu *iommu)
  85 {
  86         dmar_writeq(iommu->reg + DMAR_PQH_REG, 0ULL);
  87         dmar_writeq(iommu->reg + DMAR_PQT_REG, 0ULL);
  88         dmar_writeq(iommu->reg + DMAR_PQA_REG, 0ULL);
  89 
  90         if (iommu->pr_irq) {
  91                 free_irq(iommu->pr_irq, iommu);
  92                 dmar_free_hwirq(iommu->pr_irq);
  93                 iommu->pr_irq = 0;
  94         }
  95 
  96         free_pages((unsigned long)iommu->prq, PRQ_ORDER);
  97         iommu->prq = NULL;
  98 
  99         return 0;
 100 }
 101 
 102 static void intel_flush_svm_range_dev (struct intel_svm *svm, struct intel_svm_dev *sdev,
 103                                 unsigned long address, unsigned long pages, int ih)
 104 {
 105         struct qi_desc desc;
 106 
 107         if (pages == -1) {
 108                 desc.qw0 = QI_EIOTLB_PASID(svm->pasid) |
 109                         QI_EIOTLB_DID(sdev->did) |
 110                         QI_EIOTLB_GRAN(QI_GRAN_NONG_PASID) |
 111                         QI_EIOTLB_TYPE;
 112                 desc.qw1 = 0;
 113         } else {
 114                 int mask = ilog2(__roundup_pow_of_two(pages));
 115 
 116                 desc.qw0 = QI_EIOTLB_PASID(svm->pasid) |
 117                                 QI_EIOTLB_DID(sdev->did) |
 118                                 QI_EIOTLB_GRAN(QI_GRAN_PSI_PASID) |
 119                                 QI_EIOTLB_TYPE;
 120                 desc.qw1 = QI_EIOTLB_ADDR(address) |
 121                                 QI_EIOTLB_IH(ih) |
 122                                 QI_EIOTLB_AM(mask);
 123         }
 124         desc.qw2 = 0;
 125         desc.qw3 = 0;
 126         qi_submit_sync(&desc, svm->iommu);
 127 
 128         if (sdev->dev_iotlb) {
 129                 desc.qw0 = QI_DEV_EIOTLB_PASID(svm->pasid) |
 130                                 QI_DEV_EIOTLB_SID(sdev->sid) |
 131                                 QI_DEV_EIOTLB_QDEP(sdev->qdep) |
 132                                 QI_DEIOTLB_TYPE;
 133                 if (pages == -1) {
 134                         desc.qw1 = QI_DEV_EIOTLB_ADDR(-1ULL >> 1) |
 135                                         QI_DEV_EIOTLB_SIZE;
 136                 } else if (pages > 1) {
 137                         /* The least significant zero bit indicates the size. So,
 138                          * for example, an "address" value of 0x12345f000 will
 139                          * flush from 0x123440000 to 0x12347ffff (256KiB). */
 140                         unsigned long last = address + ((unsigned long)(pages - 1) << VTD_PAGE_SHIFT);
 141                         unsigned long mask = __rounddown_pow_of_two(address ^ last);
 142 
 143                         desc.qw1 = QI_DEV_EIOTLB_ADDR((address & ~mask) |
 144                                         (mask - 1)) | QI_DEV_EIOTLB_SIZE;
 145                 } else {
 146                         desc.qw1 = QI_DEV_EIOTLB_ADDR(address);
 147                 }
 148                 desc.qw2 = 0;
 149                 desc.qw3 = 0;
 150                 qi_submit_sync(&desc, svm->iommu);
 151         }
 152 }
 153 
 154 static void intel_flush_svm_range(struct intel_svm *svm, unsigned long address,
 155                                 unsigned long pages, int ih)
 156 {
 157         struct intel_svm_dev *sdev;
 158 
 159         rcu_read_lock();
 160         list_for_each_entry_rcu(sdev, &svm->devs, list)
 161                 intel_flush_svm_range_dev(svm, sdev, address, pages, ih);
 162         rcu_read_unlock();
 163 }
 164 
 165 /* Pages have been freed at this point */
 166 static void intel_invalidate_range(struct mmu_notifier *mn,
 167                                    struct mm_struct *mm,
 168                                    unsigned long start, unsigned long end)
 169 {
 170         struct intel_svm *svm = container_of(mn, struct intel_svm, notifier);
 171 
 172         intel_flush_svm_range(svm, start,
 173                               (end - start + PAGE_SIZE - 1) >> VTD_PAGE_SHIFT, 0);
 174 }
 175 
 176 static void intel_mm_release(struct mmu_notifier *mn, struct mm_struct *mm)
 177 {
 178         struct intel_svm *svm = container_of(mn, struct intel_svm, notifier);
 179         struct intel_svm_dev *sdev;
 180 
 181         /* This might end up being called from exit_mmap(), *before* the page
 182          * tables are cleared. And __mmu_notifier_release() will delete us from
 183          * the list of notifiers so that our invalidate_range() callback doesn't
 184          * get called when the page tables are cleared. So we need to protect
 185          * against hardware accessing those page tables.
 186          *
 187          * We do it by clearing the entry in the PASID table and then flushing
 188          * the IOTLB and the PASID table caches. This might upset hardware;
 189          * perhaps we'll want to point the PASID to a dummy PGD (like the zero
 190          * page) so that we end up taking a fault that the hardware really
 191          * *has* to handle gracefully without affecting other processes.
 192          */
 193         rcu_read_lock();
 194         list_for_each_entry_rcu(sdev, &svm->devs, list) {
 195                 intel_pasid_tear_down_entry(svm->iommu, sdev->dev, svm->pasid);
 196                 intel_flush_svm_range_dev(svm, sdev, 0, -1, 0);
 197         }
 198         rcu_read_unlock();
 199 
 200 }
 201 
 202 static const struct mmu_notifier_ops intel_mmuops = {
 203         .release = intel_mm_release,
 204         .invalidate_range = intel_invalidate_range,
 205 };
 206 
 207 static DEFINE_MUTEX(pasid_mutex);
 208 static LIST_HEAD(global_svm_list);
 209 
 210 int intel_svm_bind_mm(struct device *dev, int *pasid, int flags, struct svm_dev_ops *ops)
 211 {
 212         struct intel_iommu *iommu = intel_svm_device_to_iommu(dev);
 213         struct device_domain_info *info;
 214         struct intel_svm_dev *sdev;
 215         struct intel_svm *svm = NULL;
 216         struct mm_struct *mm = NULL;
 217         int pasid_max;
 218         int ret;
 219 
 220         if (!iommu || dmar_disabled)
 221                 return -EINVAL;
 222 
 223         if (dev_is_pci(dev)) {
 224                 pasid_max = pci_max_pasids(to_pci_dev(dev));
 225                 if (pasid_max < 0)
 226                         return -EINVAL;
 227         } else
 228                 pasid_max = 1 << 20;
 229 
 230         if (flags & SVM_FLAG_SUPERVISOR_MODE) {
 231                 if (!ecap_srs(iommu->ecap))
 232                         return -EINVAL;
 233         } else if (pasid) {
 234                 mm = get_task_mm(current);
 235                 BUG_ON(!mm);
 236         }
 237 
 238         mutex_lock(&pasid_mutex);
 239         if (pasid && !(flags & SVM_FLAG_PRIVATE_PASID)) {
 240                 struct intel_svm *t;
 241 
 242                 list_for_each_entry(t, &global_svm_list, list) {
 243                         if (t->mm != mm || (t->flags & SVM_FLAG_PRIVATE_PASID))
 244                                 continue;
 245 
 246                         svm = t;
 247                         if (svm->pasid >= pasid_max) {
 248                                 dev_warn(dev,
 249                                          "Limited PASID width. Cannot use existing PASID %d\n",
 250                                          svm->pasid);
 251                                 ret = -ENOSPC;
 252                                 goto out;
 253                         }
 254 
 255                         list_for_each_entry(sdev, &svm->devs, list) {
 256                                 if (dev == sdev->dev) {
 257                                         if (sdev->ops != ops) {
 258                                                 ret = -EBUSY;
 259                                                 goto out;
 260                                         }
 261                                         sdev->users++;
 262                                         goto success;
 263                                 }
 264                         }
 265 
 266                         break;
 267                 }
 268         }
 269 
 270         sdev = kzalloc(sizeof(*sdev), GFP_KERNEL);
 271         if (!sdev) {
 272                 ret = -ENOMEM;
 273                 goto out;
 274         }
 275         sdev->dev = dev;
 276 
 277         ret = intel_iommu_enable_pasid(iommu, dev);
 278         if (ret || !pasid) {
 279                 /* If they don't actually want to assign a PASID, this is
 280                  * just an enabling check/preparation. */
 281                 kfree(sdev);
 282                 goto out;
 283         }
 284 
 285         info = dev->archdata.iommu;
 286         if (!info || !info->pasid_supported) {
 287                 kfree(sdev);
 288                 goto out;
 289         }
 290 
 291         sdev->did = FLPT_DEFAULT_DID;
 292         sdev->sid = PCI_DEVID(info->bus, info->devfn);
 293         if (info->ats_enabled) {
 294                 sdev->dev_iotlb = 1;
 295                 sdev->qdep = info->ats_qdep;
 296                 if (sdev->qdep >= QI_DEV_EIOTLB_MAX_INVS)
 297                         sdev->qdep = 0;
 298         }
 299 
 300         /* Finish the setup now we know we're keeping it */
 301         sdev->users = 1;
 302         sdev->ops = ops;
 303         init_rcu_head(&sdev->rcu);
 304 
 305         if (!svm) {
 306                 svm = kzalloc(sizeof(*svm), GFP_KERNEL);
 307                 if (!svm) {
 308                         ret = -ENOMEM;
 309                         kfree(sdev);
 310                         goto out;
 311                 }
 312                 svm->iommu = iommu;
 313 
 314                 if (pasid_max > intel_pasid_max_id)
 315                         pasid_max = intel_pasid_max_id;
 316 
 317                 /* Do not use PASID 0 in caching mode (virtualised IOMMU) */
 318                 ret = intel_pasid_alloc_id(svm,
 319                                            !!cap_caching_mode(iommu->cap),
 320                                            pasid_max, GFP_KERNEL);
 321                 if (ret < 0) {
 322                         kfree(svm);
 323                         kfree(sdev);
 324                         goto out;
 325                 }
 326                 svm->pasid = ret;
 327                 svm->notifier.ops = &intel_mmuops;
 328                 svm->mm = mm;
 329                 svm->flags = flags;
 330                 INIT_LIST_HEAD_RCU(&svm->devs);
 331                 INIT_LIST_HEAD(&svm->list);
 332                 ret = -ENOMEM;
 333                 if (mm) {
 334                         ret = mmu_notifier_register(&svm->notifier, mm);
 335                         if (ret) {
 336                                 intel_pasid_free_id(svm->pasid);
 337                                 kfree(svm);
 338                                 kfree(sdev);
 339                                 goto out;
 340                         }
 341                 }
 342 
 343                 spin_lock(&iommu->lock);
 344                 ret = intel_pasid_setup_first_level(iommu, dev,
 345                                 mm ? mm->pgd : init_mm.pgd,
 346                                 svm->pasid, FLPT_DEFAULT_DID,
 347                                 mm ? 0 : PASID_FLAG_SUPERVISOR_MODE);
 348                 spin_unlock(&iommu->lock);
 349                 if (ret) {
 350                         if (mm)
 351                                 mmu_notifier_unregister(&svm->notifier, mm);
 352                         intel_pasid_free_id(svm->pasid);
 353                         kfree(svm);
 354                         kfree(sdev);
 355                         goto out;
 356                 }
 357 
 358                 list_add_tail(&svm->list, &global_svm_list);
 359         } else {
 360                 /*
 361                  * Binding a new device with existing PASID, need to setup
 362                  * the PASID entry.
 363                  */
 364                 spin_lock(&iommu->lock);
 365                 ret = intel_pasid_setup_first_level(iommu, dev,
 366                                                 mm ? mm->pgd : init_mm.pgd,
 367                                                 svm->pasid, FLPT_DEFAULT_DID,
 368                                                 mm ? 0 : PASID_FLAG_SUPERVISOR_MODE);
 369                 spin_unlock(&iommu->lock);
 370                 if (ret) {
 371                         kfree(sdev);
 372                         goto out;
 373                 }
 374         }
 375         list_add_rcu(&sdev->list, &svm->devs);
 376 
 377  success:
 378         *pasid = svm->pasid;
 379         ret = 0;
 380  out:
 381         mutex_unlock(&pasid_mutex);
 382         if (mm)
 383                 mmput(mm);
 384         return ret;
 385 }
 386 EXPORT_SYMBOL_GPL(intel_svm_bind_mm);
 387 
 388 int intel_svm_unbind_mm(struct device *dev, int pasid)
 389 {
 390         struct intel_svm_dev *sdev;
 391         struct intel_iommu *iommu;
 392         struct intel_svm *svm;
 393         int ret = -EINVAL;
 394 
 395         mutex_lock(&pasid_mutex);
 396         iommu = intel_svm_device_to_iommu(dev);
 397         if (!iommu)
 398                 goto out;
 399 
 400         svm = intel_pasid_lookup_id(pasid);
 401         if (!svm)
 402                 goto out;
 403 
 404         list_for_each_entry(sdev, &svm->devs, list) {
 405                 if (dev == sdev->dev) {
 406                         ret = 0;
 407                         sdev->users--;
 408                         if (!sdev->users) {
 409                                 list_del_rcu(&sdev->list);
 410                                 /* Flush the PASID cache and IOTLB for this device.
 411                                  * Note that we do depend on the hardware *not* using
 412                                  * the PASID any more. Just as we depend on other
 413                                  * devices never using PASIDs that they have no right
 414                                  * to use. We have a *shared* PASID table, because it's
 415                                  * large and has to be physically contiguous. So it's
 416                                  * hard to be as defensive as we might like. */
 417                                 intel_pasid_tear_down_entry(iommu, dev, svm->pasid);
 418                                 intel_flush_svm_range_dev(svm, sdev, 0, -1, 0);
 419                                 kfree_rcu(sdev, rcu);
 420 
 421                                 if (list_empty(&svm->devs)) {
 422                                         intel_pasid_free_id(svm->pasid);
 423                                         if (svm->mm)
 424                                                 mmu_notifier_unregister(&svm->notifier, svm->mm);
 425 
 426                                         list_del(&svm->list);
 427 
 428                                         /* We mandate that no page faults may be outstanding
 429                                          * for the PASID when intel_svm_unbind_mm() is called.
 430                                          * If that is not obeyed, subtle errors will happen.
 431                                          * Let's make them less subtle... */
 432                                         memset(svm, 0x6b, sizeof(*svm));
 433                                         kfree(svm);
 434                                 }
 435                         }
 436                         break;
 437                 }
 438         }
 439  out:
 440         mutex_unlock(&pasid_mutex);
 441 
 442         return ret;
 443 }
 444 EXPORT_SYMBOL_GPL(intel_svm_unbind_mm);
 445 
 446 int intel_svm_is_pasid_valid(struct device *dev, int pasid)
 447 {
 448         struct intel_iommu *iommu;
 449         struct intel_svm *svm;
 450         int ret = -EINVAL;
 451 
 452         mutex_lock(&pasid_mutex);
 453         iommu = intel_svm_device_to_iommu(dev);
 454         if (!iommu)
 455                 goto out;
 456 
 457         svm = intel_pasid_lookup_id(pasid);
 458         if (!svm)
 459                 goto out;
 460 
 461         /* init_mm is used in this case */
 462         if (!svm->mm)
 463                 ret = 1;
 464         else if (atomic_read(&svm->mm->mm_users) > 0)
 465                 ret = 1;
 466         else
 467                 ret = 0;
 468 
 469  out:
 470         mutex_unlock(&pasid_mutex);
 471 
 472         return ret;
 473 }
 474 EXPORT_SYMBOL_GPL(intel_svm_is_pasid_valid);
 475 
 476 /* Page request queue descriptor */
 477 struct page_req_dsc {
 478         union {
 479                 struct {
 480                         u64 type:8;
 481                         u64 pasid_present:1;
 482                         u64 priv_data_present:1;
 483                         u64 rsvd:6;
 484                         u64 rid:16;
 485                         u64 pasid:20;
 486                         u64 exe_req:1;
 487                         u64 pm_req:1;
 488                         u64 rsvd2:10;
 489                 };
 490                 u64 qw_0;
 491         };
 492         union {
 493                 struct {
 494                         u64 rd_req:1;
 495                         u64 wr_req:1;
 496                         u64 lpig:1;
 497                         u64 prg_index:9;
 498                         u64 addr:52;
 499                 };
 500                 u64 qw_1;
 501         };
 502         u64 priv_data[2];
 503 };
 504 
 505 #define PRQ_RING_MASK   ((0x1000 << PRQ_ORDER) - 0x20)
 506 
 507 static bool access_error(struct vm_area_struct *vma, struct page_req_dsc *req)
 508 {
 509         unsigned long requested = 0;
 510 
 511         if (req->exe_req)
 512                 requested |= VM_EXEC;
 513 
 514         if (req->rd_req)
 515                 requested |= VM_READ;
 516 
 517         if (req->wr_req)
 518                 requested |= VM_WRITE;
 519 
 520         return (requested & ~vma->vm_flags) != 0;
 521 }
 522 
 523 static bool is_canonical_address(u64 addr)
 524 {
 525         int shift = 64 - (__VIRTUAL_MASK_SHIFT + 1);
 526         long saddr = (long) addr;
 527 
 528         return (((saddr << shift) >> shift) == saddr);
 529 }
 530 
 531 static irqreturn_t prq_event_thread(int irq, void *d)
 532 {
 533         struct intel_iommu *iommu = d;
 534         struct intel_svm *svm = NULL;
 535         int head, tail, handled = 0;
 536 
 537         /* Clear PPR bit before reading head/tail registers, to
 538          * ensure that we get a new interrupt if needed. */
 539         writel(DMA_PRS_PPR, iommu->reg + DMAR_PRS_REG);
 540 
 541         tail = dmar_readq(iommu->reg + DMAR_PQT_REG) & PRQ_RING_MASK;
 542         head = dmar_readq(iommu->reg + DMAR_PQH_REG) & PRQ_RING_MASK;
 543         while (head != tail) {
 544                 struct intel_svm_dev *sdev;
 545                 struct vm_area_struct *vma;
 546                 struct page_req_dsc *req;
 547                 struct qi_desc resp;
 548                 int result;
 549                 vm_fault_t ret;
 550                 u64 address;
 551 
 552                 handled = 1;
 553 
 554                 req = &iommu->prq[head / sizeof(*req)];
 555 
 556                 result = QI_RESP_FAILURE;
 557                 address = (u64)req->addr << VTD_PAGE_SHIFT;
 558                 if (!req->pasid_present) {
 559                         pr_err("%s: Page request without PASID: %08llx %08llx\n",
 560                                iommu->name, ((unsigned long long *)req)[0],
 561                                ((unsigned long long *)req)[1]);
 562                         goto no_pasid;
 563                 }
 564 
 565                 if (!svm || svm->pasid != req->pasid) {
 566                         rcu_read_lock();
 567                         svm = intel_pasid_lookup_id(req->pasid);
 568                         /* It *can't* go away, because the driver is not permitted
 569                          * to unbind the mm while any page faults are outstanding.
 570                          * So we only need RCU to protect the internal idr code. */
 571                         rcu_read_unlock();
 572 
 573                         if (!svm) {
 574                                 pr_err("%s: Page request for invalid PASID %d: %08llx %08llx\n",
 575                                        iommu->name, req->pasid, ((unsigned long long *)req)[0],
 576                                        ((unsigned long long *)req)[1]);
 577                                 goto no_pasid;
 578                         }
 579                 }
 580 
 581                 result = QI_RESP_INVALID;
 582                 /* Since we're using init_mm.pgd directly, we should never take
 583                  * any faults on kernel addresses. */
 584                 if (!svm->mm)
 585                         goto bad_req;
 586 
 587                 /* If address is not canonical, return invalid response */
 588                 if (!is_canonical_address(address))
 589                         goto bad_req;
 590 
 591                 /* If the mm is already defunct, don't handle faults. */
 592                 if (!mmget_not_zero(svm->mm))
 593                         goto bad_req;
 594 
 595                 down_read(&svm->mm->mmap_sem);
 596                 vma = find_extend_vma(svm->mm, address);
 597                 if (!vma || address < vma->vm_start)
 598                         goto invalid;
 599 
 600                 if (access_error(vma, req))
 601                         goto invalid;
 602 
 603                 ret = handle_mm_fault(vma, address,
 604                                       req->wr_req ? FAULT_FLAG_WRITE : 0);
 605                 if (ret & VM_FAULT_ERROR)
 606                         goto invalid;
 607 
 608                 result = QI_RESP_SUCCESS;
 609         invalid:
 610                 up_read(&svm->mm->mmap_sem);
 611                 mmput(svm->mm);
 612         bad_req:
 613                 /* Accounting for major/minor faults? */
 614                 rcu_read_lock();
 615                 list_for_each_entry_rcu(sdev, &svm->devs, list) {
 616                         if (sdev->sid == req->rid)
 617                                 break;
 618                 }
 619                 /* Other devices can go away, but the drivers are not permitted
 620                  * to unbind while any page faults might be in flight. So it's
 621                  * OK to drop the 'lock' here now we have it. */
 622                 rcu_read_unlock();
 623 
 624                 if (WARN_ON(&sdev->list == &svm->devs))
 625                         sdev = NULL;
 626 
 627                 if (sdev && sdev->ops && sdev->ops->fault_cb) {
 628                         int rwxp = (req->rd_req << 3) | (req->wr_req << 2) |
 629                                 (req->exe_req << 1) | (req->pm_req);
 630                         sdev->ops->fault_cb(sdev->dev, req->pasid, req->addr,
 631                                             req->priv_data, rwxp, result);
 632                 }
 633                 /* We get here in the error case where the PASID lookup failed,
 634                    and these can be NULL. Do not use them below this point! */
 635                 sdev = NULL;
 636                 svm = NULL;
 637         no_pasid:
 638                 if (req->lpig || req->priv_data_present) {
 639                         /*
 640                          * Per VT-d spec. v3.0 ch7.7, system software must
 641                          * respond with page group response if private data
 642                          * is present (PDP) or last page in group (LPIG) bit
 643                          * is set. This is an additional VT-d feature beyond
 644                          * PCI ATS spec.
 645                          */
 646                         resp.qw0 = QI_PGRP_PASID(req->pasid) |
 647                                 QI_PGRP_DID(req->rid) |
 648                                 QI_PGRP_PASID_P(req->pasid_present) |
 649                                 QI_PGRP_PDP(req->pasid_present) |
 650                                 QI_PGRP_RESP_CODE(result) |
 651                                 QI_PGRP_RESP_TYPE;
 652                         resp.qw1 = QI_PGRP_IDX(req->prg_index) |
 653                                 QI_PGRP_LPIG(req->lpig);
 654 
 655                         if (req->priv_data_present)
 656                                 memcpy(&resp.qw2, req->priv_data,
 657                                        sizeof(req->priv_data));
 658                         resp.qw2 = 0;
 659                         resp.qw3 = 0;
 660                         qi_submit_sync(&resp, iommu);
 661                 }
 662                 head = (head + sizeof(*req)) & PRQ_RING_MASK;
 663         }
 664 
 665         dmar_writeq(iommu->reg + DMAR_PQH_REG, tail);
 666 
 667         return IRQ_RETVAL(handled);
 668 }