drm/xe/userptr: Hold notifier_lock for write on inject test path

When CONFIG_DRM_XE_USERPTR_INVAL_INJECT=y, xe_pt_svm_userptr_pre_commit()
runs vma_check_userptr() with the svm notifier_lock taken for read. The
test injection causes vma_check_userptr() to call
xe_vma_userptr_force_invalidate(), which feeds into
xe_vma_userptr_do_inval() with drm_gpusvm_ctx.in_notifier=true. That
flag tells drm_gpusvm_unmap_pages() the caller already holds
notifier_lock for write and only asserts the mode. Because the caller
actually holds it for read, the assertion fires:

  WARNING: drivers/gpu/drm/drm_gpusvm.c:1669 at \
           drm_gpusvm_unmap_pages+0xd4/0x130 [drm_gpusvm_helper]
  Call Trace:
   xe_vma_userptr_do_inval+0x40d/0xfd0 [xe]
   xe_vma_userptr_invalidate_pass1+0x3e6/0x8d0 [xe]
   xe_vma_userptr_force_invalidate+0xde/0x290 [xe]
   vma_check_userptr.constprop.0+0x1c6/0x220 [xe]
   xe_pt_svm_userptr_pre_commit+0x6a3/0xc60 [xe]
   ...
   xe_vm_bind_ioctl+0x3a0a/0x4480 [xe]

Acquire notifier_lock for write in pre-commit when the inject Kconfig
is enabled, via new helpers xe_pt_svm_userptr_notifier_lock()/_unlock().
Rename xe_svm_assert_held_read() to
xe_svm_assert_held_read_or_inject_write() so it asserts the correct
mode under each build configuration. Production builds
(CONFIG_DRM_XE_USERPTR_INVAL_INJECT=n) keep the existing read-mode
behavior bit-for-bit.

Fixes: 9e9787414882 ("drm/xe/userptr: replace xe_hmm with gpusvm")
Assisted-by: Claude:claude-opus-4.7
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Zongyao Bai <zongyao.bai@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20260625215615.3016892-1-shuicheng.lin@intel.com
Signed-off-by: Shuicheng Lin <shuicheng.lin@intel.com>
(cherry picked from commit 80ccbd97ffee8ad2e73167d826fe7be548364365)
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>

2 files changed, 48 insertions, 10 deletions

diff --git a/drivers/gpu/drm/xe/xe_pt.c b/drivers/gpu/drm/xe/xe_pt.c
index 234ea175c5e3..3380ce710a48 100644
--- a/drivers/gpu/drm/xe/xe_pt.c
+++ b/drivers/gpu/drm/xe/xe_pt.c
@@ -1086,7 +1086,7 @@ static void xe_pt_commit_locks_assert(struct xe_vma *vma)
 	xe_pt_commit_prepare_locks_assert(vma);
 
 	if (xe_vma_is_userptr(vma))
-		xe_svm_assert_held_read(vm);
+		xe_svm_assert_held_read_or_inject_write(vm);
 }
 
 static void xe_pt_commit(struct xe_vma *vma,
@@ -1406,6 +1406,33 @@ static int xe_pt_pre_commit(struct xe_migrate_pt_update *pt_update)
 				     pt_update_ops, rftree);
 }
 
+/*
+ * Acquire/release the svm notifier_lock around xe_pt_svm_userptr_pre_commit()
+ * and the matching late release in xe_pt_update_ops_run(). Read mode by
+ * default; write mode when CONFIG_DRM_XE_USERPTR_INVAL_INJECT is on,
+ * because a userptr op in this critical section may invoke the injected
+ * xe_vma_userptr_force_invalidate() path that calls
+ * drm_gpusvm_unmap_pages() with ctx->in_notifier=true, which requires the
+ * lock held for write.
+ */
+static void xe_pt_svm_userptr_notifier_lock(struct xe_vm *vm)
+{
+#if IS_ENABLED(CONFIG_DRM_XE_USERPTR_INVAL_INJECT)
+	down_write(&vm->svm.gpusvm.notifier_lock);
+#else
+	xe_svm_notifier_lock(vm);
+#endif
+}
+
+static void xe_pt_svm_userptr_notifier_unlock(struct xe_vm *vm)
+{
+#if IS_ENABLED(CONFIG_DRM_XE_USERPTR_INVAL_INJECT)
+	up_write(&vm->svm.gpusvm.notifier_lock);
+#else
+	xe_svm_notifier_unlock(vm);
+#endif
+}
+
 #if IS_ENABLED(CONFIG_DRM_GPUSVM)
 #ifdef CONFIG_DRM_XE_USERPTR_INVAL_INJECT
 
@@ -1437,7 +1464,7 @@ static int vma_check_userptr(struct xe_vm *vm, struct xe_vma *vma,
 	struct xe_userptr_vma *uvma;
 	unsigned long notifier_seq;
 
-	xe_svm_assert_held_read(vm);
+	xe_svm_assert_held_read_or_inject_write(vm);
 
 	if (!xe_vma_is_userptr(vma))
 		return 0;
@@ -1467,7 +1494,7 @@ static int op_check_svm_userptr(struct xe_vm *vm, struct xe_vma_op *op,
 {
 	int err = 0;
 
-	xe_svm_assert_held_read(vm);
+	xe_svm_assert_held_read_or_inject_write(vm);
 
 	switch (op->base.op) {
 	case DRM_GPUVA_OP_MAP:
@@ -1539,12 +1566,12 @@ static int xe_pt_svm_userptr_pre_commit(struct xe_migrate_pt_update *pt_update)
 	if (err)
 		return err;
 
-	xe_svm_notifier_lock(vm);
+	xe_pt_svm_userptr_notifier_lock(vm);
 
 	list_for_each_entry(op, &vops->list, link) {
 		err = op_check_svm_userptr(vm, op, pt_update_ops);
 		if (err) {
-			xe_svm_notifier_unlock(vm);
+			xe_pt_svm_userptr_notifier_unlock(vm);
 			break;
 		}
 	}
@@ -2403,7 +2430,7 @@ static void bind_op_commit(struct xe_vm *vm, struct xe_tile *tile,
 			   vma->tile_invalidated & ~BIT(tile->id));
 	vma->tile_staged &= ~BIT(tile->id);
 	if (xe_vma_is_userptr(vma)) {
-		xe_svm_assert_held_read(vm);
+		xe_svm_assert_held_read_or_inject_write(vm);
 		to_userptr_vma(vma)->userptr.initial_bind = true;
 	}
 
@@ -2439,7 +2466,7 @@ static void unbind_op_commit(struct xe_vm *vm, struct xe_tile *tile,
 	if (!vma->tile_present) {
 		list_del_init(&vma->combined_links.rebind);
 		if (xe_vma_is_userptr(vma)) {
-			xe_svm_assert_held_read(vm);
+			xe_svm_assert_held_read_or_inject_write(vm);
 
 			spin_lock(&vm->userptr.invalidated_lock);
 			list_del_init(&to_userptr_vma(vma)->userptr.invalidate_link);
@@ -2715,7 +2742,7 @@ xe_pt_update_ops_run(struct xe_tile *tile, struct xe_vma_ops *vops)
 	}
 
 	if (pt_update_ops->needs_svm_lock)
-		xe_svm_notifier_unlock(vm);
+		xe_pt_svm_userptr_notifier_unlock(vm);
 
 	/*
 	 * The last fence is only used for zero bind queue idling; migrate
diff --git a/drivers/gpu/drm/xe/xe_svm.h b/drivers/gpu/drm/xe/xe_svm.h
index b7b8eeacf196..3ca46a6f98c7 100644
--- a/drivers/gpu/drm/xe/xe_svm.h
+++ b/drivers/gpu/drm/xe/xe_svm.h
@@ -394,8 +394,19 @@ static inline struct drm_pagemap *xe_drm_pagemap_from_fd(int fd, u32 region_inst
 #define xe_svm_assert_in_notifier(vm__) \
 	lockdep_assert_held_write(&(vm__)->svm.gpusvm.notifier_lock)
 
-#define xe_svm_assert_held_read(vm__) \
+/*
+ * Assert the svm notifier_lock is held. Read mode by default; write mode
+ * when CONFIG_DRM_XE_USERPTR_INVAL_INJECT is on, because that path forces
+ * a userptr invalidation that ends in drm_gpusvm_unmap_pages() with
+ * ctx->in_notifier=true, which requires the lock held for write.
+ */
+#if IS_ENABLED(CONFIG_DRM_XE_USERPTR_INVAL_INJECT)
+#define xe_svm_assert_held_read_or_inject_write(vm__) \
+	lockdep_assert_held_write(&(vm__)->svm.gpusvm.notifier_lock)
+#else
+#define xe_svm_assert_held_read_or_inject_write(vm__) \
 	lockdep_assert_held_read(&(vm__)->svm.gpusvm.notifier_lock)
+#endif
 
 #define xe_svm_notifier_lock(vm__)	\
 	drm_gpusvm_notifier_lock(&(vm__)->svm.gpusvm)
@@ -409,7 +420,7 @@ static inline struct drm_pagemap *xe_drm_pagemap_from_fd(int fd, u32 region_inst
 #else
 #define xe_svm_assert_in_notifier(...) do {} while (0)
 
-static inline void xe_svm_assert_held_read(struct xe_vm *vm)
+static inline void xe_svm_assert_held_read_or_inject_write(struct xe_vm *vm)
 {
 }