[PATCH v3 3/5] drm/amdgpu: introduce SVM range migration decision layer

[Junhua Shen <Junhua.Shen@amd.com>]

Add the migration decision infrastructure for drm_pagemap-based SVM
VRAM migration:

- Define enum amdgpu_svm_migrate_mode (NONE, TO_VRAM, TO_SYSMEM,
  PREFERRED) to carry migration intent
- Implement amdgpu_svm_range_migrate_range() which handles both
  directions: TO_VRAM via drm_pagemap_populate_mm(), TO_SYSMEM via
  drm_gpusvm_range_evict()

Signed-off-by: Junhua Shen <Junhua.Shen@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/Makefile           |   6 +-
 .../drm/amd/amdgpu/amdgpu_svm_range_migrate.c | 140 ++++++++++++++++++
 .../drm/amd/amdgpu/amdgpu_svm_range_migrate.h |  60 ++++++++
 3 files changed, 203 insertions(+), 3 deletions(-)
 create mode 100644 drivers/gpu/drm/amd/amdgpu/amdgpu_svm_range_migrate.c
 create mode 100644 drivers/gpu/drm/amd/amdgpu/amdgpu_svm_range_migrate.h

diff --git a/drivers/gpu/drm/amd/amdgpu/Makefile b/drivers/gpu/drm/amd/amdgpu/Makefile
index e64abb5c8ab8..cf4f453b7e68 100644
--- a/drivers/gpu/drm/amd/amdgpu/Makefile
+++ b/drivers/gpu/drm/amd/amdgpu/Makefile
@@ -323,14 +323,14 @@ amdgpu-$(CONFIG_HMM_MIRROR) += amdgpu_hmm.o
 
 # svm support
 amdgpu-$(CONFIG_DRM_AMDGPU_SVM) += amdgpu_svm.o amdgpu_svm_attr.o \
-	amdgpu_svm_range.o amdgpu_migrate.o
+	amdgpu_svm_range.o amdgpu_svm_range_migrate.o amdgpu_migrate.o
 
 .PHONY: clean-svm
 clean-svm:
 	rm -f $(obj)/amdgpu_svm.o $(obj)/amdgpu_svm_attr.o $(obj)/amdgpu_svm_range.o \
-	      $(obj)/amdgpu_migrate.o \
+	      $(obj)/amdgpu_svm_range_migrate.o $(obj)/amdgpu_migrate.o \
 	      $(obj)/.amdgpu_svm.o.cmd $(obj)/.amdgpu_svm_attr.o.cmd $(obj)/.amdgpu_svm_range.o.cmd \
-	      $(obj)/.amdgpu_migrate.o.cmd
+	      $(obj)/.amdgpu_svm_range_migrate.o.cmd $(obj)/.amdgpu_migrate.o.cmd
 
 include $(FULL_AMD_PATH)/pm/Makefile
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_svm_range_migrate.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_svm_range_migrate.c
new file mode 100644
index 000000000000..f29d4cdb5c64
--- /dev/null
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_svm_range_migrate.c
@@ -0,0 +1,140 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+/*
+ * Copyright 2026 Advanced Micro Devices, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+#include "amdgpu.h"
+#include "amdgpu_svm.h"
+#include "amdgpu_svm_range.h"
+#include "amdgpu_migrate.h"
+#include "amdgpu_svm_range_migrate.h"
+
+static bool
+range_in_vram(struct drm_gpusvm_range *range)
+{
+	struct drm_gpusvm_pages_flags flags = {
+		/* Pairs with WRITE_ONCE in drm_gpusvm_get_pages() */
+		.__flags = READ_ONCE(range->pages.flags.__flags),
+	};
+
+	return flags.has_devmem_pages;
+}
+
+static struct drm_pagemap *
+amdgpu_svm_get_dpagemap(struct amdgpu_svm *svm)
+{
+	struct amdgpu_pagemap *apagemap = svm->adev->apagemap;
+
+	if (!apagemap->initialized)
+		return NULL;
+
+	return &apagemap->dpagemap;
+}
+
+static bool
+range_needs_migrate_to_vram(struct drm_gpusvm_range *range,
+			    enum amdgpu_svm_migrate_mode mode)
+{
+	if (!range->pages.flags.migrate_devmem)
+		return false;
+
+	if (mode == AMDGPU_SVM_MIGRATE_TO_SYSMEM)
+		return false;
+
+	if (range_in_vram(range))
+		return false;
+
+	return true;
+}
+
+/**
+ * amdgpu_svm_range_migrate_to_vram - Migrate a single range's pages to VRAM
+ * @svm: Pointer to the AMDGPU SVM structure
+ * @range: Pointer to the GPU SVM range to migrate
+ *
+ * Return: 0 on success, negative errno on failure
+ */
+static int
+amdgpu_svm_range_migrate_to_vram(struct amdgpu_svm *svm,
+				  struct drm_gpusvm_range *range)
+{
+	struct drm_pagemap *dpagemap = amdgpu_svm_get_dpagemap(svm);
+	unsigned long start = drm_gpusvm_range_start(range);
+	unsigned long end = drm_gpusvm_range_end(range);
+	int ret;
+
+	if (!dpagemap)
+		return -ENODEV;
+
+	ret = drm_pagemap_populate_mm(dpagemap, start, end,
+				      svm->gpusvm.mm, 0);
+	if (ret) {
+		AMDGPU_SVM_TRACE("migrate_to_vram failed: ret=%d [0x%lx-0x%lx]\n",
+				 ret, start, end);
+		return ret;
+	}
+
+	return 0;
+}
+
+bool
+amdgpu_pagemap_capable(struct amdgpu_svm *svm)
+{
+	if (svm->adev->gmc.is_app_apu)
+		return false;
+
+	if (!amdgpu_svm_get_dpagemap(svm))
+		return false;
+
+	return true;
+}
+
+/**
+ * amdgpu_svm_range_migrate_range - Per-range migration
+ * @svm: Pointer to the AMDGPU SVM structure
+ * @range: The GPU SVM range to migrate
+ * @migrate_mode: Migration intent
+ *
+ * NOTE: Only AMDGPU_SVM_MIGRATE_TO_VRAM and
+ * AMDGPU_SVM_MIGRATE_TO_SYSMEM are valid inputs. Passing any other
+ * migrate mode will trigger a WARN_ON() and the function will return
+ * -EINVAL. The caller should resolve PREFERRED/OTHER higher-level
+ * intents into one of the two concrete directions before calling this
+ * helper.
+ */
+int
+amdgpu_svm_range_migrate_range(struct amdgpu_svm *svm,
+			       struct drm_gpusvm_range *range,
+			       enum amdgpu_svm_migrate_mode migrate_mode)
+{
+	if (WARN_ON(migrate_mode != AMDGPU_SVM_MIGRATE_TO_VRAM &&
+		    migrate_mode != AMDGPU_SVM_MIGRATE_TO_SYSMEM))
+		return -EINVAL;
+
+	if (range_needs_migrate_to_vram(range, migrate_mode))
+		return amdgpu_svm_range_migrate_to_vram(svm, range);
+	else if (migrate_mode == AMDGPU_SVM_MIGRATE_TO_SYSMEM &&
+	    range_in_vram(range))
+		return drm_gpusvm_range_evict(&svm->gpusvm, range);
+
+	return 0;
+}
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_svm_range_migrate.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_svm_range_migrate.h
new file mode 100644
index 000000000000..eba0b5f90e6e
--- /dev/null
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_svm_range_migrate.h
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+/*
+ * Copyright 2026 Advanced Micro Devices, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+#ifndef __AMDGPU_SVM_RANGE_MIGRATE_H__
+#define __AMDGPU_SVM_RANGE_MIGRATE_H__
+
+struct amdgpu_svm;
+struct drm_gpusvm_range;
+
+/**
+ * enum amdgpu_svm_migrate_mode - Migration mode for SVM range migration
+ *
+ * @AMDGPU_SVM_MIGRATE_NONE: No migration requested. Callers use it to
+ *	skip the migration call and allow early-out for already-mapped ranges.
+ *
+ * @AMDGPU_SVM_MIGRATE_TO_VRAM: Migrate pages to VRAM before mapping.
+ *
+ * @AMDGPU_SVM_MIGRATE_TO_SYSMEM: Evict VRAM pages back to system memory.
+ *
+ * @AMDGPU_SVM_MIGRATE_PREFERRED: Follow preferred_loc to decide migration.
+ * Callers resolve this to TO_VRAM or TO_SYSMEM before calling
+ * amdgpu_svm_range_migrate_range().
+ *
+ * Only TO_VRAM and TO_SYSMEM are valid inputs to
+ * amdgpu_svm_range_migrate_range().
+ */
+enum amdgpu_svm_migrate_mode {
+	AMDGPU_SVM_MIGRATE_NONE,
+	AMDGPU_SVM_MIGRATE_TO_VRAM,
+	AMDGPU_SVM_MIGRATE_TO_SYSMEM,
+	AMDGPU_SVM_MIGRATE_PREFERRED
+};
+
+bool amdgpu_pagemap_capable(struct amdgpu_svm *svm);
+int amdgpu_svm_range_migrate_range(struct amdgpu_svm *svm,
+				    struct drm_gpusvm_range *range,
+				    enum amdgpu_svm_migrate_mode migrate_mode);
+
+#endif /* __AMDGPU_SVM_RANGE_MIGRATE_H__ */
-- 
2.34.1