]> git.ipfire.org Git - thirdparty/linux.git/commitdiff
drm/xe: Strict migration policy for atomic SVM faults
authorMatthew Brost <matthew.brost@intel.com>
Mon, 12 May 2025 13:54:56 +0000 (06:54 -0700)
committerLucas De Marchi <lucas.demarchi@intel.com>
Wed, 14 May 2025 16:03:29 +0000 (09:03 -0700)
Mixing GPU and CPU atomics does not work unless a strict migration
policy of GPU atomics must be device memory. Enforce a policy of must be
in VRAM with a retry loop of 3 attempts, if retry loop fails abort
fault.

Removing always_migrate_to_vram modparam as we now have real migration
policy.

v2:
 - Only retry migration on atomics
 - Drop alway migrate modparam
v3:
 - Only set vram_only on DGFX (Himal)
 - Bail on get_pages failure if vram_only and retry count exceeded (Himal)
 - s/vram_only/devmem_only
 - Update xe_svm_range_is_valid to accept devmem_only argument
v4:
 - Fix logic bug get_pages failure
v5:
 - Fix commit message (Himal)
 - Mention removing always_migrate_to_vram in commit message (Lucas)
 - Fix xe_svm_range_is_valid to check for devmem pages
 - Bail on devmem_only && !migrate_devmem (Thomas)
v6:
 - Add READ_ONCE barriers for opportunistic checks (Thomas)
 - Pair READ_ONCE with WRITE_ONCE (Thomas)
v7:
 - Adjust comments (Thomas)

Fixes: 2f118c949160 ("drm/xe: Add SVM VRAM migration")
Cc: stable@vger.kernel.org
Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Acked-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://lore.kernel.org/r/20250512135500.1405019-3-matthew.brost@intel.com
(cherry picked from commit a9ac0fa455b050d03e3032501368048fb284d318)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
drivers/gpu/drm/drm_gpusvm.c
drivers/gpu/drm/xe/xe_module.c
drivers/gpu/drm/xe/xe_module.h
drivers/gpu/drm/xe/xe_pt.c
drivers/gpu/drm/xe/xe_svm.c
drivers/gpu/drm/xe/xe_svm.h
include/drm/drm_gpusvm.h

index a58d03e6cac277526344b156f7e5c9840cada6d6..41f6616bcf76fa99fa85198d8e2deb51fcd1a087 100644 (file)
@@ -1118,6 +1118,10 @@ static void __drm_gpusvm_range_unmap_pages(struct drm_gpusvm *gpusvm,
        lockdep_assert_held(&gpusvm->notifier_lock);
 
        if (range->flags.has_dma_mapping) {
+               struct drm_gpusvm_range_flags flags = {
+                       .__flags = range->flags.__flags,
+               };
+
                for (i = 0, j = 0; i < npages; j++) {
                        struct drm_pagemap_device_addr *addr = &range->dma_addr[j];
 
@@ -1131,8 +1135,12 @@ static void __drm_gpusvm_range_unmap_pages(struct drm_gpusvm *gpusvm,
                                                            dev, *addr);
                        i += 1 << addr->order;
                }
-               range->flags.has_devmem_pages = false;
-               range->flags.has_dma_mapping = false;
+
+               /* WRITE_ONCE pairs with READ_ONCE for opportunistic checks */
+               flags.has_devmem_pages = false;
+               flags.has_dma_mapping = false;
+               WRITE_ONCE(range->flags.__flags, flags.__flags);
+
                range->dpagemap = NULL;
        }
 }
@@ -1334,6 +1342,7 @@ int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
        int err = 0;
        struct dev_pagemap *pagemap;
        struct drm_pagemap *dpagemap;
+       struct drm_gpusvm_range_flags flags;
 
 retry:
        hmm_range.notifier_seq = mmu_interval_read_begin(notifier);
@@ -1378,7 +1387,8 @@ map_pages:
         */
        drm_gpusvm_notifier_lock(gpusvm);
 
-       if (range->flags.unmapped) {
+       flags.__flags = range->flags.__flags;
+       if (flags.unmapped) {
                drm_gpusvm_notifier_unlock(gpusvm);
                err = -EFAULT;
                goto err_free;
@@ -1474,14 +1484,17 @@ map_pages:
                }
                i += 1 << order;
                num_dma_mapped = i;
-               range->flags.has_dma_mapping = true;
+               flags.has_dma_mapping = true;
        }
 
        if (zdd) {
-               range->flags.has_devmem_pages = true;
+               flags.has_devmem_pages = true;
                range->dpagemap = dpagemap;
        }
 
+       /* WRITE_ONCE pairs with READ_ONCE for opportunistic checks */
+       WRITE_ONCE(range->flags.__flags, flags.__flags);
+
        drm_gpusvm_notifier_unlock(gpusvm);
        kvfree(pfns);
 set_seqno:
index 9f4632e39a1ad5776557633af06749c0c5606e78..e861c694f3361bf0de4161c8ae7a065d2edaf94b 100644 (file)
@@ -29,9 +29,6 @@ struct xe_modparam xe_modparam = {
 module_param_named(svm_notifier_size, xe_modparam.svm_notifier_size, uint, 0600);
 MODULE_PARM_DESC(svm_notifier_size, "Set the svm notifier size(in MiB), must be power of 2");
 
-module_param_named(always_migrate_to_vram, xe_modparam.always_migrate_to_vram, bool, 0444);
-MODULE_PARM_DESC(always_migrate_to_vram, "Always migrate to VRAM on GPU fault");
-
 module_param_named_unsafe(force_execlist, xe_modparam.force_execlist, bool, 0444);
 MODULE_PARM_DESC(force_execlist, "Force Execlist submission");
 
index 84339e509c80d634f1365748f832c1d78ff70b56..5a3bfea8b7b4c4b2cdbad318670ea7ebd4346697 100644 (file)
@@ -12,7 +12,6 @@
 struct xe_modparam {
        bool force_execlist;
        bool probe_display;
-       bool always_migrate_to_vram;
        u32 force_vram_bar_size;
        int guc_log_level;
        char *guc_firmware_path;
index ffaf0d02dc7de9632168072e2bbc35d385eed5f1..856038553b812a0d9b8160beb4129d67a4af1354 100644 (file)
@@ -2232,11 +2232,19 @@ static void op_commit(struct xe_vm *vm,
        }
        case DRM_GPUVA_OP_DRIVER:
        {
+               /* WRITE_ONCE pairs with READ_ONCE in xe_svm.c */
+
                if (op->subop == XE_VMA_SUBOP_MAP_RANGE) {
-                       op->map_range.range->tile_present |= BIT(tile->id);
-                       op->map_range.range->tile_invalidated &= ~BIT(tile->id);
+                       WRITE_ONCE(op->map_range.range->tile_present,
+                                  op->map_range.range->tile_present |
+                                  BIT(tile->id));
+                       WRITE_ONCE(op->map_range.range->tile_invalidated,
+                                  op->map_range.range->tile_invalidated &
+                                  ~BIT(tile->id));
                } else if (op->subop == XE_VMA_SUBOP_UNMAP_RANGE) {
-                       op->unmap_range.range->tile_present &= ~BIT(tile->id);
+                       WRITE_ONCE(op->unmap_range.range->tile_present,
+                                  op->unmap_range.range->tile_present &
+                                  ~BIT(tile->id));
                }
                break;
        }
index 24c578e1170e40fb7705951e79a7184bff68c236..e65d3b820ee024cbcc19c59a2636a36822ef4cac 100644 (file)
 
 static bool xe_svm_range_in_vram(struct xe_svm_range *range)
 {
-       /* Not reliable without notifier lock */
-       return range->base.flags.has_devmem_pages;
+       /*
+        * Advisory only check whether the range is currently backed by VRAM
+        * memory.
+        */
+
+       struct drm_gpusvm_range_flags flags = {
+               /* Pairs with WRITE_ONCE in drm_gpusvm.c */
+               .__flags = READ_ONCE(range->base.flags.__flags),
+       };
+
+       return flags.has_devmem_pages;
 }
 
 static bool xe_svm_range_has_vram_binding(struct xe_svm_range *range)
@@ -645,9 +654,16 @@ void xe_svm_fini(struct xe_vm *vm)
 }
 
 static bool xe_svm_range_is_valid(struct xe_svm_range *range,
-                                 struct xe_tile *tile)
+                                 struct xe_tile *tile,
+                                 bool devmem_only)
 {
-       return (range->tile_present & ~range->tile_invalidated) & BIT(tile->id);
+       /*
+        * Advisory only check whether the range currently has a valid mapping,
+        * READ_ONCE pairs with WRITE_ONCE in xe_pt.c
+        */
+       return ((READ_ONCE(range->tile_present) &
+                ~READ_ONCE(range->tile_invalidated)) & BIT(tile->id)) &&
+               (!devmem_only || xe_svm_range_in_vram(range));
 }
 
 static struct xe_vram_region *tile_to_vr(struct xe_tile *tile)
@@ -712,6 +728,36 @@ unlock:
        return err;
 }
 
+static bool supports_4K_migration(struct xe_device *xe)
+{
+       if (xe->info.vram_flags & XE_VRAM_FLAGS_NEED64K)
+               return false;
+
+       return true;
+}
+
+static bool xe_svm_range_needs_migrate_to_vram(struct xe_svm_range *range,
+                                              struct xe_vma *vma)
+{
+       struct xe_vm *vm = range_to_vm(&range->base);
+       u64 range_size = xe_svm_range_size(range);
+
+       if (!range->base.flags.migrate_devmem)
+               return false;
+
+       if (xe_svm_range_in_vram(range)) {
+               drm_dbg(&vm->xe->drm, "Range is already in VRAM\n");
+               return false;
+       }
+
+       if (range_size <= SZ_64K && !supports_4K_migration(vm->xe)) {
+               drm_dbg(&vm->xe->drm, "Platform doesn't support SZ_4K range migration\n");
+               return false;
+       }
+
+       return true;
+}
+
 /**
  * xe_svm_handle_pagefault() - SVM handle page fault
  * @vm: The VM.
@@ -735,11 +781,14 @@ int xe_svm_handle_pagefault(struct xe_vm *vm, struct xe_vma *vma,
                        IS_ENABLED(CONFIG_DRM_XE_DEVMEM_MIRROR),
                .check_pages_threshold = IS_DGFX(vm->xe) &&
                        IS_ENABLED(CONFIG_DRM_XE_DEVMEM_MIRROR) ? SZ_64K : 0,
+               .devmem_only = atomic && IS_DGFX(vm->xe) &&
+                       IS_ENABLED(CONFIG_DRM_XE_DEVMEM_MIRROR),
        };
        struct xe_svm_range *range;
        struct drm_gpusvm_range *r;
        struct drm_exec exec;
        struct dma_fence *fence;
+       int migrate_try_count = ctx.devmem_only ? 3 : 1;
        ktime_t end = 0;
        int err;
 
@@ -758,24 +807,30 @@ retry:
        if (IS_ERR(r))
                return PTR_ERR(r);
 
+       if (ctx.devmem_only && !r->flags.migrate_devmem)
+               return -EACCES;
+
        range = to_xe_range(r);
-       if (xe_svm_range_is_valid(range, tile))
+       if (xe_svm_range_is_valid(range, tile, ctx.devmem_only))
                return 0;
 
        range_debug(range, "PAGE FAULT");
 
-       /* XXX: Add migration policy, for now migrate range once */
-       if (!range->skip_migrate && range->base.flags.migrate_devmem &&
-           xe_svm_range_size(range) >= SZ_64K) {
-               range->skip_migrate = true;
-
+       if (--migrate_try_count >= 0 &&
+           xe_svm_range_needs_migrate_to_vram(range, vma)) {
                err = xe_svm_alloc_vram(vm, tile, range, &ctx);
                if (err) {
-                       drm_dbg(&vm->xe->drm,
-                               "VRAM allocation failed, falling back to "
-                               "retrying fault, asid=%u, errno=%pe\n",
-                               vm->usm.asid, ERR_PTR(err));
-                       goto retry;
+                       if (migrate_try_count || !ctx.devmem_only) {
+                               drm_dbg(&vm->xe->drm,
+                                       "VRAM allocation failed, falling back to retrying fault, asid=%u, errno=%pe\n",
+                                       vm->usm.asid, ERR_PTR(err));
+                               goto retry;
+                       } else {
+                               drm_err(&vm->xe->drm,
+                                       "VRAM allocation failed, retry count exceeded, asid=%u, errno=%pe\n",
+                                       vm->usm.asid, ERR_PTR(err));
+                               return err;
+                       }
                }
        }
 
@@ -783,15 +838,22 @@ retry:
        err = drm_gpusvm_range_get_pages(&vm->svm.gpusvm, r, &ctx);
        /* Corner where CPU mappings have changed */
        if (err == -EOPNOTSUPP || err == -EFAULT || err == -EPERM) {
-               if (err == -EOPNOTSUPP) {
-                       range_debug(range, "PAGE FAULT - EVICT PAGES");
-                       drm_gpusvm_range_evict(&vm->svm.gpusvm, &range->base);
+               if (migrate_try_count > 0 || !ctx.devmem_only) {
+                       if (err == -EOPNOTSUPP) {
+                               range_debug(range, "PAGE FAULT - EVICT PAGES");
+                               drm_gpusvm_range_evict(&vm->svm.gpusvm,
+                                                      &range->base);
+                       }
+                       drm_dbg(&vm->xe->drm,
+                               "Get pages failed, falling back to retrying, asid=%u, gpusvm=%p, errno=%pe\n",
+                               vm->usm.asid, &vm->svm.gpusvm, ERR_PTR(err));
+                       range_debug(range, "PAGE FAULT - RETRY PAGES");
+                       goto retry;
+               } else {
+                       drm_err(&vm->xe->drm,
+                               "Get pages failed, retry count exceeded, asid=%u, gpusvm=%p, errno=%pe\n",
+                               vm->usm.asid, &vm->svm.gpusvm, ERR_PTR(err));
                }
-               drm_dbg(&vm->xe->drm,
-                       "Get pages failed, falling back to retrying, asid=%u, gpusvm=%p, errno=%pe\n",
-                       vm->usm.asid, &vm->svm.gpusvm, ERR_PTR(err));
-               range_debug(range, "PAGE FAULT - RETRY PAGES");
-               goto retry;
        }
        if (err) {
                range_debug(range, "PAGE FAULT - FAIL PAGE COLLECT");
@@ -825,9 +887,6 @@ retry_bind:
        }
        drm_exec_fini(&exec);
 
-       if (xe_modparam.always_migrate_to_vram)
-               range->skip_migrate = false;
-
        dma_fence_wait(fence, false);
        dma_fence_put(fence);
 
index be306fe7aaa4b323e74abc0ad55b0718f5972c57..fe58ac2f4baaca41cce4314d8e6b4d781b84661e 100644 (file)
@@ -36,11 +36,6 @@ struct xe_svm_range {
         * range. Protected by GPU SVM notifier lock.
         */
        u8 tile_invalidated;
-       /**
-        * @skip_migrate: Skip migration to VRAM, protected by GPU fault handler
-        * locking.
-        */
-       u8 skip_migrate :1;
 };
 
 #if IS_ENABLED(CONFIG_DRM_GPUSVM)
index 9fd25fc880a4927f8bc1aff47af639d7d98e8a8a..653d48dbe1c11afee8e63ca4b88162fb58aa6f84 100644 (file)
@@ -185,6 +185,31 @@ struct drm_gpusvm_notifier {
        } flags;
 };
 
+/**
+ * struct drm_gpusvm_range_flags - Structure representing a GPU SVM range flags
+ *
+ * @migrate_devmem: Flag indicating whether the range can be migrated to device memory
+ * @unmapped: Flag indicating if the range has been unmapped
+ * @partial_unmap: Flag indicating if the range has been partially unmapped
+ * @has_devmem_pages: Flag indicating if the range has devmem pages
+ * @has_dma_mapping: Flag indicating if the range has a DMA mapping
+ * @__flags: Flags for range in u16 form (used for READ_ONCE)
+ */
+struct drm_gpusvm_range_flags {
+       union {
+               struct {
+                       /* All flags below must be set upon creation */
+                       u16 migrate_devmem : 1;
+                       /* All flags below must be set / cleared under notifier lock */
+                       u16 unmapped : 1;
+                       u16 partial_unmap : 1;
+                       u16 has_devmem_pages : 1;
+                       u16 has_dma_mapping : 1;
+               };
+               u16 __flags;
+       };
+};
+
 /**
  * struct drm_gpusvm_range - Structure representing a GPU SVM range
  *
@@ -198,11 +223,6 @@ struct drm_gpusvm_notifier {
  * @dpagemap: The struct drm_pagemap of the device pages we're dma-mapping.
  *            Note this is assuming only one drm_pagemap per range is allowed.
  * @flags: Flags for range
- * @flags.migrate_devmem: Flag indicating whether the range can be migrated to device memory
- * @flags.unmapped: Flag indicating if the range has been unmapped
- * @flags.partial_unmap: Flag indicating if the range has been partially unmapped
- * @flags.has_devmem_pages: Flag indicating if the range has devmem pages
- * @flags.has_dma_mapping: Flag indicating if the range has a DMA mapping
  *
  * This structure represents a GPU SVM range used for tracking memory ranges
  * mapped in a DRM device.
@@ -216,15 +236,7 @@ struct drm_gpusvm_range {
        unsigned long notifier_seq;
        struct drm_pagemap_device_addr *dma_addr;
        struct drm_pagemap *dpagemap;
-       struct {
-               /* All flags below must be set upon creation */
-               u16 migrate_devmem : 1;
-               /* All flags below must be set / cleared under notifier lock */
-               u16 unmapped : 1;
-               u16 partial_unmap : 1;
-               u16 has_devmem_pages : 1;
-               u16 has_dma_mapping : 1;
-       } flags;
+       struct drm_gpusvm_range_flags flags;
 };
 
 /**