drm/gpusvm, drm/xe: Fix userptr to not allow device private pages

When userptr is used on SVM-enabled VMs, a non-NULL
hmm_range::dev_private_owner value might mean that
hmm_range_fault() attempts to return device private pages.
Either that will fail, or the userptr code will not know
how to handle those.

Use NULL for hmm_range::dev_private_owner to migrate
such pages to system. In order to do that, move the
struct drm_gpusvm::device_private_page_owner field to
struct drm_gpusvm_ctx::device_private_page_owner so that
it doesn't remain immutable over the drm_gpusvm lifetime.

v2:
- Don't conditionally compile xe_svm_devm_owner().
- Kerneldoc xe_svm_devm_owner().

Fixes: 9e9787414882 ("drm/xe/userptr: replace xe_hmm with gpusvm")
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://lore.kernel.org/r/20250930122752.96034-1-thomas.hellstrom@linux.intel.com
(cherry picked from commit ad298d9ec957414dbf3d51f3c8bca4b6d2416c0c)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

4 files changed, 19 insertions, 8 deletions

diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
index 7f2f1f041f1d..7e2db71ff34e 100644
--- a/drivers/gpu/drm/xe/xe_svm.c
+++ b/drivers/gpu/drm/xe/xe_svm.c
@@ -67,11 +67,6 @@ void xe_svm_range_debug(struct xe_svm_range *range, const char *operation)
 	range_debug(range, operation);
 }
 
-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)
 {
@@ -744,15 +739,14 @@ 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, xe_svm_devm_owner(vm->xe), 0,
-				      vm->size,
+				      current->mm, 0, vm->size,
 				      xe_modparam.svm_notifier_size * SZ_1M,
 				      &gpusvm_ops, fault_chunk_sizes,
 				      ARRAY_SIZE(fault_chunk_sizes));
 		drm_gpusvm_driver_set_lock(&vm->svm.gpusvm, &vm->lock);
 	} else {
 		err = drm_gpusvm_init(&vm->svm.gpusvm, "Xe SVM (simple)",
-				      &vm->xe->drm, NULL, NULL, 0, 0, 0, NULL,
+				      &vm->xe->drm, NULL, 0, 0, 0, NULL,
 				      NULL, 0);
 	}
 
@@ -1017,6 +1011,7 @@ static int __xe_svm_handle_pagefault(struct xe_vm *vm, struct xe_vma *vma,
 		.devmem_only = need_vram && devmem_possible,
 		.timeslice_ms = need_vram && devmem_possible ?
 			vm->xe->atomic_svm_timeslice_ms : 0,
+		.device_private_page_owner = xe_svm_devm_owner(vm->xe),
 	};
 	struct xe_validation_ctx vctx;
 	struct drm_exec exec;
diff --git a/drivers/gpu/drm/xe/xe_svm.h b/drivers/gpu/drm/xe/xe_svm.h
index cef6ee7d6fe3..0955d2ac8d74 100644
--- a/drivers/gpu/drm/xe/xe_svm.h
+++ b/drivers/gpu/drm/xe/xe_svm.h
@@ -6,6 +6,20 @@
 #ifndef _XE_SVM_H_
 #define _XE_SVM_H_
 
+struct xe_device;
+
+/**
+ * xe_svm_devm_owner() - Return the owner of device private memory
+ * @xe: The xe device.
+ *
+ * Return: The owner of this device's device private memory to use in
+ * hmm_range_fault()-
+ */
+static inline void *xe_svm_devm_owner(struct xe_device *xe)
+{
+	return xe;
+}
+
 #if IS_ENABLED(CONFIG_DRM_XE_GPUSVM)
 
 #include <drm/drm_pagemap.h>
diff --git a/drivers/gpu/drm/xe/xe_userptr.c b/drivers/gpu/drm/xe/xe_userptr.c
index 91d09af71ced..f16e92cd8090 100644
--- a/drivers/gpu/drm/xe/xe_userptr.c
+++ b/drivers/gpu/drm/xe/xe_userptr.c
@@ -54,6 +54,7 @@ int xe_vma_userptr_pin_pages(struct xe_userptr_vma *uvma)
 	struct xe_device *xe = vm->xe;
 	struct drm_gpusvm_ctx ctx = {
 		.read_only = xe_vma_read_only(vma),
+		.device_private_page_owner = NULL,
 	};
 
 	lockdep_assert_held(&vm->lock);
diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index 0cacab20ff85..027e6ce648c5 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -2881,6 +2881,7 @@ static int prefetch_ranges(struct xe_vm *vm, struct xe_vma_op *op)
 	ctx.read_only = xe_vma_read_only(vma);
 	ctx.devmem_possible = devmem_possible;
 	ctx.check_pages_threshold = devmem_possible ? SZ_64K : 0;
+	ctx.device_private_page_owner = xe_svm_devm_owner(vm->xe);
 
 	/* TODO: Threading the migration */
 	xa_for_each(&op->prefetch_range.range, i, svm_range) {