drm/gpuvm: drm_gpuvm_bo_obtain() requires lock and staged mode

In commit 9ce4aef9a5b1 ("drm/gpuvm: take GEM lock inside
drm_gpuvm_bo_obtain_prealloc()") we update
drm_gpuvm_bo_obtain_prealloc() to take locks internally, which means
that it's only usable in immediate mode.

In this commit, we notice that drm_gpuvm_bo_obtain() requires you to use
staged mode. This means that we now have one variant of obtain for each
mode you might use gpuvm in.

To reflect this information, we add a warning about using it in
immediate mode, and to make the distinction clearer we rename the method
with a _locked() suffix so that it's clear that it requires the caller
to take the locks.

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20260108-gpuvm-rust-v2-2-dbd014005a0b@google.com
[ Slightly reword commit message to refer to commit 9ce4aef9a5b1
  ("drm/gpuvm: take GEM lock inside drm_gpuvm_bo_obtain_prealloc()").
  - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

6 files changed, 19 insertions, 9 deletions

diff --git a/drivers/gpu/drm/drm_gpuvm.c b/drivers/gpu/drm/drm_gpuvm.c
index 8a06d296561d..9826fc013d67 100644
--- a/drivers/gpu/drm/drm_gpuvm.c
+++ b/drivers/gpu/drm/drm_gpuvm.c
@@ -1825,16 +1825,26 @@ EXPORT_SYMBOL_GPL(drm_gpuvm_bo_find);
  * count of the &drm_gpuvm_bo accordingly. If not found, allocates a new
  * &drm_gpuvm_bo.
  *
+ * Requires the lock for the GEMs gpuva list.
+ *
  * A new &drm_gpuvm_bo is added to the GEMs gpuva list.
  *
  * Returns: a pointer to the &drm_gpuvm_bo on success, an ERR_PTR on failure
  */
 struct drm_gpuvm_bo *
-drm_gpuvm_bo_obtain(struct drm_gpuvm *gpuvm,
-		    struct drm_gem_object *obj)
+drm_gpuvm_bo_obtain_locked(struct drm_gpuvm *gpuvm,
+			   struct drm_gem_object *obj)
 {
 	struct drm_gpuvm_bo *vm_bo;
 
+	/*
+	 * In immediate mode this would require the caller to hold the GEMs
+	 * gpuva mutex, but it's not okay to allocate while holding that lock,
+	 * and this method allocates. Immediate mode drivers should use
+	 * drm_gpuvm_bo_obtain_prealloc() instead.
+	 */
+	drm_WARN_ON(gpuvm->drm, drm_gpuvm_immediate_mode(gpuvm));
+
 	vm_bo = drm_gpuvm_bo_find(gpuvm, obj);
 	if (vm_bo)
 		return vm_bo;
@@ -1848,7 +1858,7 @@ drm_gpuvm_bo_obtain(struct drm_gpuvm *gpuvm,
 
 	return vm_bo;
 }
-EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain);
+EXPORT_SYMBOL_GPL(drm_gpuvm_bo_obtain_locked);
 
 /**
  * drm_gpuvm_bo_obtain_prealloc() - obtains an instance of the &drm_gpuvm_bo
diff --git a/drivers/gpu/drm/imagination/pvr_vm.c b/drivers/gpu/drm/imagination/pvr_vm.c
index 48e52c5561be..9a9ad4e82305 100644
--- a/drivers/gpu/drm/imagination/pvr_vm.c
+++ b/drivers/gpu/drm/imagination/pvr_vm.c
@@ -256,7 +256,7 @@ pvr_vm_bind_op_map_init(struct pvr_vm_bind_op *bind_op,
 	bind_op->type = PVR_VM_BIND_TYPE_MAP;
 
 	dma_resv_lock(obj->resv, NULL);
-	bind_op->gpuvm_bo = drm_gpuvm_bo_obtain(&vm_ctx->gpuvm_mgr, obj);
+	bind_op->gpuvm_bo = drm_gpuvm_bo_obtain_locked(&vm_ctx->gpuvm_mgr, obj);
 	dma_resv_unlock(obj->resv);
 	if (IS_ERR(bind_op->gpuvm_bo))
 		return PTR_ERR(bind_op->gpuvm_bo);
diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h
index a4cf31853c50..26dfe3d22e3e 100644
--- a/drivers/gpu/drm/msm/msm_gem.h
+++ b/drivers/gpu/drm/msm/msm_gem.h
@@ -60,7 +60,7 @@ struct msm_gem_vm_log_entry {
  * embedded in any larger driver structure.  The GEM object holds a list of
  * drm_gpuvm_bo, which in turn holds a list of msm_gem_vma.  A linked vma
  * holds a reference to the vm_bo, and drops it when the vma is unlinked.
- * So we just need to call drm_gpuvm_bo_obtain() to return a ref to an
+ * So we just need to call drm_gpuvm_bo_obtain_locked() to return a ref to an
  * existing vm_bo, or create a new one.  Once the vma is linked, the ref
  * to the vm_bo can be dropped (since the vma is holding one).
  */
diff --git a/drivers/gpu/drm/msm/msm_gem_vma.c b/drivers/gpu/drm/msm/msm_gem_vma.c
index 71d5238437eb..71943104ce9f 100644
--- a/drivers/gpu/drm/msm/msm_gem_vma.c
+++ b/drivers/gpu/drm/msm/msm_gem_vma.c
@@ -413,7 +413,7 @@ msm_gem_vma_new(struct drm_gpuvm *gpuvm, struct drm_gem_object *obj,
 	if (!obj)
 		return &vma->base;
 
-	vm_bo = drm_gpuvm_bo_obtain(&vm->base, obj);
+	vm_bo = drm_gpuvm_bo_obtain_locked(&vm->base, obj);
 	if (IS_ERR(vm_bo)) {
 		ret = PTR_ERR(vm_bo);
 		goto err_va_remove;
diff --git a/drivers/gpu/drm/nouveau/nouveau_uvmm.c b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
index f10809115c56..0d693760d222 100644
--- a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
@@ -1275,7 +1275,7 @@ nouveau_uvmm_bind_job_submit(struct nouveau_job *job,
 				return -ENOENT;
 
 			dma_resv_lock(obj->resv, NULL);
-			op->vm_bo = drm_gpuvm_bo_obtain(&uvmm->base, obj);
+			op->vm_bo = drm_gpuvm_bo_obtain_locked(&uvmm->base, obj);
 			dma_resv_unlock(obj->resv);
 			if (IS_ERR(op->vm_bo))
 				return PTR_ERR(op->vm_bo);
diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index 7cac646bdf1c..0e7f82eb38fc 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -1022,7 +1022,7 @@ static struct xe_vma *xe_vma_create(struct xe_vm *vm,
 
 		xe_bo_assert_held(bo);
 
-		vm_bo = drm_gpuvm_bo_obtain(vma->gpuva.vm, &bo->ttm.base);
+		vm_bo = drm_gpuvm_bo_obtain_locked(vma->gpuva.vm, &bo->ttm.base);
 		if (IS_ERR(vm_bo)) {
 			xe_vma_free(vma);
 			return ERR_CAST(vm_bo);
@@ -2269,7 +2269,7 @@ vm_bind_ioctl_ops_create(struct xe_vm *vm, struct xe_vma_ops *vops,
 		if (err)
 			return ERR_PTR(err);
 
-		vm_bo = drm_gpuvm_bo_obtain(&vm->gpuvm, obj);
+		vm_bo = drm_gpuvm_bo_obtain_locked(&vm->gpuvm, obj);
 		if (IS_ERR(vm_bo)) {
 			xe_bo_unlock(bo);
 			return ERR_CAST(vm_bo);