drm/xe/vm: Add helper to check for default VMA memory attributes

Introduce a new helper function `xe_vma_has_default_mem_attrs()` to
determine whether a VMA's memory attributes are set to their default
values. This includes checks for atomic access, PAT index, and preferred
location.

Also, add a new field `default_pat_index` to `struct xe_vma_mem_attr`
to track the initial PAT index set during the first bind. This helps
distinguish between default and user-modified pat index, such as those
changed via madvise.

Reviewed-by: Matthew Brost <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Himal Prasad Ghimiray <[e-mail]>

drivers/gpu/drm/xe/xe_vm.c

···
 	return err;
 }
 
+/**
+ * xe_vma_has_default_mem_attrs - Check if a VMA has default memory attributes
+ * @vma: Pointer to the xe_vma structure to check
+ *
+ * This function determines whether the given VMA (Virtual Memory Area)
+ * has its memory attributes set to their default values. Specifically,
+ * it checks the following conditions:
+ *
+ * - `atomic_access` is `DRM_XE_VMA_ATOMIC_UNDEFINED`
+ * - `pat_index` is equal to `default_pat_index`
+ * - `preferred_loc.devmem_fd` is `DRM_XE_PREFERRED_LOC_DEFAULT_DEVICE`
+ * - `preferred_loc.migration_policy` is `DRM_XE_MIGRATE_ALL_PAGES`
+ *
+ * Return: true if all attributes are at their default values, false otherwise.
+ */
+bool xe_vma_has_default_mem_attrs(struct xe_vma *vma)
+{
+	return (vma->attr.atomic_access == DRM_XE_ATOMIC_UNDEFINED &&
+		vma->attr.pat_index ==  vma->attr.default_pat_index &&
+		vma->attr.preferred_loc.devmem_fd == DRM_XE_PREFERRED_LOC_DEFAULT_DEVICE &&
+		vma->attr.preferred_loc.migration_policy == DRM_XE_MIGRATE_ALL_PAGES);
+}
+
 static int vm_bind_ioctl_ops_parse(struct xe_vm *vm, struct drm_gpuva_ops *ops,
 				   struct xe_vma_ops *vops)
 {
···
 					.migration_policy = DRM_XE_MIGRATE_ALL_PAGES,
 				},
 				.atomic_access = DRM_XE_ATOMIC_UNDEFINED,
+				.default_pat_index = op->map.pat_index,
 				.pat_index = op->map.pat_index,
 			};
 

drivers/gpu/drm/xe/xe_vm.h

···
 struct xe_vma *
 xe_vm_find_overlapping_vma(struct xe_vm *vm, u64 start, u64 range);
 
+bool xe_vma_has_default_mem_attrs(struct xe_vma *vma);
+
 /**
  * xe_vm_has_scratch() - Whether the vm is configured for scratch PTEs
  * @vm: The vm

drivers/gpu/drm/xe/xe_vm_types.h

···
 	u32 atomic_access;
 
 	/**
+	 * @default_pat_index: The pat index for VMA set during first bind by user.
+	 */
+	u16 default_pat_index;
+
+	/**
 	 * @pat_index: The pat index to use when encoding the PTEs for this vma.
+	 * same as default_pat_index unless overwritten by madvise.
 	 */
 	u16 pat_index;
 };