drm/xe: Add modparam for SVM notifier size

Useful to experiment with notifier size and how it affects performance.

v3:
 - Pull missing changes including in following patch (Thomas)
v5:
 - Spell out power of 2 (Thomas)

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/20250306012657.3505757-31-matthew.brost@intel.com

drivers/gpu/drm/xe/xe_module.c

@@ -22,9 +22,13 @@ struct xe_modparam xe_modparam = {
 	.guc_log_level = 3,
 	.force_probe = CONFIG_DRM_XE_FORCE_PROBE,
 	.wedged_mode = 1,
+	.svm_notifier_size = 512,
 	/* the rest are 0 by default */
 };
 
+module_param_named(svm_notifier_size, xe_modparam.svm_notifier_size, uint, 0600);
+MODULE_PARM_DESC(svm_notifier_size, "Set the svm notifier size(in MiB), must be power of 2");
+
 module_param_named_unsafe(force_execlist, xe_modparam.force_execlist, bool, 0444);
 MODULE_PARM_DESC(force_execlist, "Force Execlist submission");
 

drivers/gpu/drm/xe/xe_module.h

@@ -22,6 +22,7 @@ struct xe_modparam {
 	unsigned int max_vfs;
 #endif
 	int wedged_mode;
+	u32 svm_notifier_size;
 };
 
 extern struct xe_modparam xe_modparam;

drivers/gpu/drm/xe/xe_svm.c

@@ -6,6 +6,7 @@
 #include "xe_bo.h"
 #include "xe_gt_tlb_invalidation.h"
 #include "xe_migrate.h"
+#include "xe_module.h"
 #include "xe_pt.h"
 #include "xe_svm.h"
 #include "xe_ttm_vram_mgr.h"
@@ -607,7 +608,8 @@ int xe_svm_init(struct xe_vm *vm)
 
 	err = drm_gpusvm_init(&vm->svm.gpusvm, "Xe SVM", &vm->xe->drm,
 			      current->mm, xe_svm_devm_owner(vm->xe), 0,
-			      vm->size, SZ_512M, &gpusvm_ops, fault_chunk_sizes,
+			      vm->size, xe_modparam.svm_notifier_size * SZ_1M,
+			      &gpusvm_ops, fault_chunk_sizes,
 			      ARRAY_SIZE(fault_chunk_sizes));
 	if (err)
 		return err;