drm/xe: Add SVM device memory mirroring

Add SVM device memory mirroring which enables device pages for
migration. Enabled via CONFIG_XE_DEVMEM_MIRROR Kconfig. Kconfig option
defaults to enabled. If not enabled, SVM will work sans migration and
KMD memory footprint will be less.

v3:
 - Add CONFIG_XE_DEVMEM_MIRROR
v4:
 - Fix Kconfig (Himal)
 - Use %pe to print errors (Thomas)
 - Fix alignment issue (Checkpatch)
v5:
 - s/xe_mem_region/xe_vram_region (Rebase)
v6:
 - Only compile if CONFIG_DRM_GPUSVM selected (CI, Lucas)
 - s/drm_info/drm_dbg/

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>
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250306012657.3505757-22-matthew.brost@intel.com

drivers/gpu/drm/xe/Kconfig

@@ -74,6 +74,15 @@ config DRM_XE_DP_TUNNEL
 
 	  If in doubt say "Y".
 
+config DRM_XE_DEVMEM_MIRROR
+	bool "Enable device memory mirror"
+	depends on DRM_XE
+	select GET_FREE_REGION
+	default y
+	help
+	  Disable this option only if you want to compile out without device
+	  memory mirror. Will reduce KMD memory footprint when disabled.
+
 config DRM_XE_FORCE_PROBE
 	string "Force probe xe for selected Intel hardware IDs"
 	depends on DRM_XE

drivers/gpu/drm/xe/xe_device_types.h

@@ -106,6 +106,14 @@ struct xe_vram_region {
 	resource_size_t actual_physical_size;
 	/** @mapping: pointer to VRAM mappable space */
 	void __iomem *mapping;
+	/** @pagemap: Used to remap device memory as ZONE_DEVICE */
+	struct dev_pagemap pagemap;
+	/**
+	 * @hpa_base: base host physical address
+	 *
+	 * This is generated when remap device memory as ZONE_DEVICE
+	 */
+	resource_size_t hpa_base;
 	/** @ttm: VRAM TTM manager */
 	struct xe_ttm_vram_mgr ttm;
 };

drivers/gpu/drm/xe/xe_svm.c

@@ -29,6 +29,11 @@ static unsigned long xe_svm_range_end(struct xe_svm_range *range)
 	return drm_gpusvm_range_end(&range->base);
 }
 
+static void *xe_svm_devm_owner(struct xe_device *xe)
+{
+	return xe;
+}
+
 static struct drm_gpusvm_range *
 xe_svm_range_alloc(struct drm_gpusvm *gpusvm)
 {
@@ -313,8 +318,8 @@ int xe_svm_init(struct xe_vm *vm)
 		  xe_svm_garbage_collector_work_func);
 
 	err = drm_gpusvm_init(&vm->svm.gpusvm, "Xe SVM", &vm->xe->drm,
-			      current->mm, NULL, 0, vm->size,
-			      SZ_512M, &gpusvm_ops, fault_chunk_sizes,
+			      current->mm, xe_svm_devm_owner(vm->xe), 0,
+			      vm->size, SZ_512M, &gpusvm_ops, fault_chunk_sizes,
 			      ARRAY_SIZE(fault_chunk_sizes));
 	if (err)
 		return err;
@@ -449,3 +454,56 @@ bool xe_svm_has_mapping(struct xe_vm *vm, u64 start, u64 end)
 {
 	return drm_gpusvm_has_mapping(&vm->svm.gpusvm, start, end);
 }
+
+#if IS_ENABLED(CONFIG_DRM_XE_DEVMEM_MIRROR)
+/**
+ * xe_devm_add: Remap and provide memmap backing for device memory
+ * @tile: tile that the memory region belongs to
+ * @vr: vram memory region to remap
+ *
+ * This remap device memory to host physical address space and create
+ * struct page to back device memory
+ *
+ * Return: 0 on success standard error code otherwise
+ */
+int xe_devm_add(struct xe_tile *tile, struct xe_vram_region *vr)
+{
+	struct xe_device *xe = tile_to_xe(tile);
+	struct device *dev = &to_pci_dev(xe->drm.dev)->dev;
+	struct resource *res;
+	void *addr;
+	int ret;
+
+	res = devm_request_free_mem_region(dev, &iomem_resource,
+					   vr->usable_size);
+	if (IS_ERR(res)) {
+		ret = PTR_ERR(res);
+		return ret;
+	}
+
+	vr->pagemap.type = MEMORY_DEVICE_PRIVATE;
+	vr->pagemap.range.start = res->start;
+	vr->pagemap.range.end = res->end;
+	vr->pagemap.nr_range = 1;
+	vr->pagemap.ops = drm_gpusvm_pagemap_ops_get();
+	vr->pagemap.owner = xe_svm_devm_owner(xe);
+	addr = devm_memremap_pages(dev, &vr->pagemap);
+	if (IS_ERR(addr)) {
+		devm_release_mem_region(dev, res->start, resource_size(res));
+		ret = PTR_ERR(addr);
+		drm_err(&xe->drm, "Failed to remap tile %d memory, errno %pe\n",
+			tile->id, ERR_PTR(ret));
+		return ret;
+	}
+	vr->hpa_base = res->start;
+
+	drm_dbg(&xe->drm, "Added tile %d memory [%llx-%llx] to devm, remapped to %pr\n",
+		tile->id, vr->io_start, vr->io_start + vr->usable_size, res);
+	return 0;
+}
+#else
+int xe_devm_add(struct xe_tile *tile, struct xe_vram_region *vr)
+{
+	return 0;
+}
+#endif

drivers/gpu/drm/xe/xe_svm.h

@@ -11,6 +11,7 @@
 
 #define XE_INTERCONNECT_VRAM DRM_INTERCONNECT_DRIVER
 
+struct xe_vram_region;
 struct xe_tile;
 struct xe_vm;
 struct xe_vma;
@@ -48,6 +49,8 @@ static inline bool xe_svm_range_pages_valid(struct xe_svm_range *range)
 	return drm_gpusvm_range_pages_valid(range->base.gpusvm, &range->base);
 }
 
+int xe_devm_add(struct xe_tile *tile, struct xe_vram_region *vr);
+
 int xe_svm_init(struct xe_vm *vm);
 
 void xe_svm_fini(struct xe_vm *vm);
@@ -65,6 +68,12 @@ static inline bool xe_svm_range_pages_valid(struct xe_svm_range *range)
 	return false;
 }
 
+static inline
+int xe_devm_add(struct xe_tile *tile, struct xe_vram_region *vr)
+{
+	return 0;
+}
+
 static inline
 int xe_svm_init(struct xe_vm *vm)
 {

drivers/gpu/drm/xe/xe_tile.c

@@ -13,6 +13,7 @@
 #include "xe_migrate.h"
 #include "xe_pcode.h"
 #include "xe_sa.h"
+#include "xe_svm.h"
 #include "xe_tile.h"
 #include "xe_tile_sysfs.h"
 #include "xe_ttm_vram_mgr.h"
@@ -160,6 +161,7 @@ static int tile_ttm_mgr_init(struct xe_tile *tile)
  */
 int xe_tile_init_noalloc(struct xe_tile *tile)
 {
+	struct xe_device *xe = tile_to_xe(tile);
 	int err;
 
 	err = tile_ttm_mgr_init(tile);
@@ -168,6 +170,9 @@ int xe_tile_init_noalloc(struct xe_tile *tile)
 
 	xe_wa_apply_tile_workarounds(tile);
 
+	if (xe->info.has_usm && IS_DGFX(xe))
+		xe_devm_add(tile, &tile->mem.vram);
+
 	return xe_tile_sysfs_init(tile);
 }