drm/xe: Add Xe SVM populate_devmem_pfn GPU SVM vfunc

Get device pfns from BO's buddy blocks. Used in migrate_* core MM
functions called in GPU SVM to migrate between device and system memory.

v2:
 - Use new drm_gpusvm_devmem_ops
v3:
 - Better commit message (Thomas)
v5:
 - s/xe_mem_region/xe_vram_region (Rebase)

Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
Signed-off-by: Oak Zeng <oak.zeng@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250306012657.3505757-26-matthew.brost@intel.com

Author: mbrost05

drivers/gpu/drm/xe/xe_svm.c

@@ -7,6 +7,7 @@
 #include "xe_migrate.h"
 #include "xe_pt.h"
 #include "xe_svm.h"
+#include "xe_ttm_vram_mgr.h"
 #include "xe_vm.h"
 #include "xe_vm_types.h"
 
@@ -461,8 +462,47 @@ static int xe_svm_copy_to_ram(struct page **pages, dma_addr_t *dma_addr,
 	return xe_svm_copy(pages, dma_addr, npages, XE_SVM_COPY_TO_SRAM);
 }
 
+static struct xe_bo *to_xe_bo(struct drm_gpusvm_devmem *devmem_allocation)
+{
+	return container_of(devmem_allocation, struct xe_bo, devmem_allocation);
+}
+
+static u64 block_offset_to_pfn(struct xe_vram_region *vr, u64 offset)
+{
+	return PHYS_PFN(offset + vr->hpa_base);
+}
+
+static struct drm_buddy *tile_to_buddy(struct xe_tile *tile)
+{
+	return &tile->mem.vram.ttm.mm;
+}
+
+static int xe_svm_populate_devmem_pfn(struct drm_gpusvm_devmem *devmem_allocation,
+				      unsigned long npages, unsigned long *pfn)
+{
+	struct xe_bo *bo = to_xe_bo(devmem_allocation);
+	struct ttm_resource *res = bo->ttm.resource;
+	struct list_head *blocks = &to_xe_ttm_vram_mgr_resource(res)->blocks;
+	struct drm_buddy_block *block;
+	int j = 0;
+
+	list_for_each_entry(block, blocks, link) {
+		struct xe_vram_region *vr = block->private;
+		struct xe_tile *tile = vr_to_tile(vr);
+		struct drm_buddy *buddy = tile_to_buddy(tile);
+		u64 block_pfn = block_offset_to_pfn(vr, drm_buddy_block_offset(block));
+		int i;
+
+		for (i = 0; i < drm_buddy_block_size(buddy, block) >> PAGE_SHIFT; ++i)
+			pfn[j++] = block_pfn + i;
+	}
+
+	return 0;
+}
+
 __maybe_unused
 static const struct drm_gpusvm_devmem_ops gpusvm_devmem_ops = {
+	.populate_devmem_pfn = xe_svm_populate_devmem_pfn,
 	.copy_to_devmem = xe_svm_copy_to_devmem,
 	.copy_to_ram = xe_svm_copy_to_ram,
 };