drm/i915/gem: Migrate to system at dma-buf attach time (v7)

Until we support p2p dma or as a complement to that, migrate data
to system memory at dma-buf attach time if possible.

v2:
- Rebase on dynamic exporter. Update the igt_dmabuf_import_same_driver
  selftest to migrate if we are LMEM capable.
v3:
- Migrate also in the pin() callback.
v4:
- Migrate in attach
v5: (jason)
- Lock around the migration
v6: (jason)
- Move the can_migrate check outside the lock
- Rework the selftests to test more migration conditions.  In
  particular, SMEM, LMEM, and LMEM+SMEM are all checked.
v7: (mauld)
- Misc style nits
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210723172142.3273510-9-jason@jlekstrand.net

drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c

@@ -164,8 +164,29 @@ static int i915_gem_dmabuf_attach(struct dma_buf *dmabuf,
 				  struct dma_buf_attachment *attach)
 {
 	struct drm_i915_gem_object *obj = dma_buf_to_obj(dmabuf);
+	struct i915_gem_ww_ctx ww;
+	int err;
+
+	if (!i915_gem_object_can_migrate(obj, INTEL_REGION_SMEM))
+		return -EOPNOTSUPP;
+
+	for_i915_gem_ww(&ww, err, true) {
+		err = i915_gem_object_lock(obj, &ww);
+		if (err)
+			continue;
+
+		err = i915_gem_object_migrate(obj, &ww, INTEL_REGION_SMEM);
+		if (err)
+			continue;
 
-	return i915_gem_object_pin_pages_unlocked(obj);
+		err = i915_gem_object_wait_migration(obj, 0);
+		if (err)
+			continue;
+
+		err = i915_gem_object_pin_pages(obj);
+	}
+
+	return err;
 }
 
 static void i915_gem_dmabuf_detach(struct dma_buf *dmabuf,

drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c

@@ -85,9 +85,63 @@ static int igt_dmabuf_import_self(void *arg)
 	return err;
 }
 
-static int igt_dmabuf_import_same_driver(void *arg)
+static int igt_dmabuf_import_same_driver_lmem(void *arg)
 {
 	struct drm_i915_private *i915 = arg;
+	struct intel_memory_region *lmem = i915->mm.regions[INTEL_REGION_LMEM];
+	struct drm_i915_gem_object *obj;
+	struct drm_gem_object *import;
+	struct dma_buf *dmabuf;
+	int err;
+
+	if (!lmem)
+		return 0;
+
+	force_different_devices = true;
+
+	obj = __i915_gem_object_create_user(i915, PAGE_SIZE, &lmem, 1);
+	if (IS_ERR(obj)) {
+		pr_err("__i915_gem_object_create_user failed with err=%ld\n",
+		       PTR_ERR(dmabuf));
+		err = PTR_ERR(obj);
+		goto out_ret;
+	}
+
+	dmabuf = i915_gem_prime_export(&obj->base, 0);
+	if (IS_ERR(dmabuf)) {
+		pr_err("i915_gem_prime_export failed with err=%ld\n",
+		       PTR_ERR(dmabuf));
+		err = PTR_ERR(dmabuf);
+		goto out;
+	}
+
+	/*
+	 * We expect an import of an LMEM-only object to fail with
+	 * -EOPNOTSUPP because it can't be migrated to SMEM.
+	 */
+	import = i915_gem_prime_import(&i915->drm, dmabuf);
+	if (!IS_ERR(import)) {
+		drm_gem_object_put(import);
+		pr_err("i915_gem_prime_import succeeded when it shouldn't have\n");
+		err = -EINVAL;
+	} else if (PTR_ERR(import) != -EOPNOTSUPP) {
+		pr_err("i915_gem_prime_import failed with the wrong err=%ld\n",
+		       PTR_ERR(import));
+		err = PTR_ERR(import);
+	}
+
+	dma_buf_put(dmabuf);
+out:
+	i915_gem_object_put(obj);
+out_ret:
+	force_different_devices = false;
+	return err;
+}
+
+static int igt_dmabuf_import_same_driver(struct drm_i915_private *i915,
+					 struct intel_memory_region **regions,
+					 unsigned int num_regions)
+{
 	struct drm_i915_gem_object *obj, *import_obj;
 	struct drm_gem_object *import;
 	struct dma_buf *dmabuf;
@@ -97,8 +151,12 @@ static int igt_dmabuf_import_same_driver(void *arg)
 	int err;
 
 	force_different_devices = true;
-	obj = i915_gem_object_create_shmem(i915, PAGE_SIZE);
+
+	obj = __i915_gem_object_create_user(i915, PAGE_SIZE,
+					    regions, num_regions);
 	if (IS_ERR(obj)) {
+		pr_err("__i915_gem_object_create_user failed with err=%ld\n",
+		       PTR_ERR(dmabuf));
 		err = PTR_ERR(obj);
 		goto out_ret;
 	}
@@ -180,6 +238,27 @@ static int igt_dmabuf_import_same_driver(void *arg)
 	return err;
 }
 
+static int igt_dmabuf_import_same_driver_smem(void *arg)
+{
+	struct drm_i915_private *i915 = arg;
+	struct intel_memory_region *smem = i915->mm.regions[INTEL_REGION_SMEM];
+
+	return igt_dmabuf_import_same_driver(i915, &smem, 1);
+}
+
+static int igt_dmabuf_import_same_driver_lmem_smem(void *arg)
+{
+	struct drm_i915_private *i915 = arg;
+	struct intel_memory_region *regions[2];
+
+	if (!i915->mm.regions[INTEL_REGION_LMEM])
+		return 0;
+
+	regions[0] = i915->mm.regions[INTEL_REGION_LMEM];
+	regions[1] = i915->mm.regions[INTEL_REGION_SMEM];
+	return igt_dmabuf_import_same_driver(i915, regions, 2);
+}
+
 static int igt_dmabuf_import(void *arg)
 {
 	struct drm_i915_private *i915 = arg;
@@ -390,7 +469,9 @@ int i915_gem_dmabuf_live_selftests(struct drm_i915_private *i915)
 {
 	static const struct i915_subtest tests[] = {
 		SUBTEST(igt_dmabuf_export),
-		SUBTEST(igt_dmabuf_import_same_driver),
+		SUBTEST(igt_dmabuf_import_same_driver_lmem),
+		SUBTEST(igt_dmabuf_import_same_driver_smem),
+		SUBTEST(igt_dmabuf_import_same_driver_lmem_smem),
 	};
 
 	return i915_subtests(tests, i915);