drm/xe: Timeslice GPU on atomic SVM fault

Ensure GPU can make forward progress on an atomic SVM GPU fault by
giving the GPU a timeslice of 5ms

v2:
 - Reduce timeslice to 5ms
 - Double timeslice on retry
 - Split out GPU SVM changes into independent patch
v5:
 - Double timeslice in a few more places

Fixes: 2f118c9 ("drm/xe: Add SVM VRAM migration")
Cc: stable@vger.kernel.org
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Link: https://lore.kernel.org/r/20250512135500.1405019-5-matthew.brost@intel.com
(cherry picked from commit a5d8d3b)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

Author: mbrost05

drivers/gpu/drm/xe/xe_svm.c

@@ -783,6 +783,8 @@ int xe_svm_handle_pagefault(struct xe_vm *vm, struct xe_vma *vma,
 			IS_ENABLED(CONFIG_DRM_XE_DEVMEM_MIRROR) ? SZ_64K : 0,
 		.devmem_only = atomic && IS_DGFX(vm->xe) &&
 			IS_ENABLED(CONFIG_DRM_XE_DEVMEM_MIRROR),
+		.timeslice_ms = atomic && IS_DGFX(vm->xe) &&
+			IS_ENABLED(CONFIG_DRM_XE_DEVMEM_MIRROR) ? 5 : 0,
 	};
 	struct xe_svm_range *range;
 	struct drm_gpusvm_range *r;
@@ -819,6 +821,7 @@ int xe_svm_handle_pagefault(struct xe_vm *vm, struct xe_vma *vma,
 	if (--migrate_try_count >= 0 &&
 	    xe_svm_range_needs_migrate_to_vram(range, vma)) {
 		err = xe_svm_alloc_vram(vm, tile, range, &ctx);
+		ctx.timeslice_ms <<= 1;	/* Double timeslice if we have to retry */
 		if (err) {
 			if (migrate_try_count || !ctx.devmem_only) {
 				drm_dbg(&vm->xe->drm,
@@ -838,6 +841,7 @@ int xe_svm_handle_pagefault(struct xe_vm *vm, struct xe_vma *vma,
 	err = drm_gpusvm_range_get_pages(&vm->svm.gpusvm, r, &ctx);
 	/* Corner where CPU mappings have changed */
 	if (err == -EOPNOTSUPP || err == -EFAULT || err == -EPERM) {
+		ctx.timeslice_ms <<= 1;	/* Double timeslice if we have to retry */
 		if (migrate_try_count > 0 || !ctx.devmem_only) {
 			if (err == -EOPNOTSUPP) {
 				range_debug(range, "PAGE FAULT - EVICT PAGES");
@@ -877,6 +881,7 @@ int xe_svm_handle_pagefault(struct xe_vm *vm, struct xe_vma *vma,
 			drm_exec_fini(&exec);
 			err = PTR_ERR(fence);
 			if (err == -EAGAIN) {
+				ctx.timeslice_ms <<= 1;	/* Double timeslice if we have to retry */
 				range_debug(range, "PAGE FAULT - RETRY BIND");
 				goto retry;
 			}