[PATCH v2 2/3] drm/gpuvm: drm_gpuvm_bo_obtain() requires lock and staged mode

[Alice Ryhl <aliceryhl@google.com>]

In the previous commit we updated 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>
---
 drivers/gpu/drm/drm_gpuvm.c            | 16 +++++++++++++---
 drivers/gpu/drm/imagination/pvr_vm.c   |  2 +-
 drivers/gpu/drm/msm/msm_gem.h          |  2 +-
 drivers/gpu/drm/msm/msm_gem_vma.c      |  2 +-
 drivers/gpu/drm/nouveau/nouveau_uvmm.c |  2 +-
 drivers/gpu/drm/xe/xe_vm.c             |  4 ++--
 include/drm/drm_gpuvm.h                |  4 ++--
 7 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/drm_gpuvm.c b/drivers/gpu/drm/drm_gpuvm.c
index 0de47e83d84df11a53e40fe82d069882e46149b6..37f0d97f653466285f036a5bf0246a5fea0234cd 100644
--- a/drivers/gpu/drm/drm_gpuvm.c
+++ b/drivers/gpu/drm/drm_gpuvm.c
@@ -1844,16 +1844,26 @@ 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;
@@ -1867,7 +1877,7 @@ 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 48e52c5561beb4ca3070ef3f2f4337225fafc124..9a9ad4e82305d23ce4741b59f09951265365c1de 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 a4cf31853c5008e171c3ad72cde1004c60fe5212..26dfe3d22e3e847f7e63174481d03f72878a8ced 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 71d5238437eb89b23c067cca3c01cb86c94b934b..71943104ce9fd01d89e781d41bf067a98a574c5f 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 f10809115c563a12c6f6e798bf9fe77a0a3a993c..0d693760d2223be9a141ee4b8d820269ae4868b6 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 7cac646bdf1c03689bca9511f5e1f40270811622..0e7f82eb38fc90e1b42ffc1cdf49a6b202fbb3e5 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);
diff --git a/include/drm/drm_gpuvm.h b/include/drm/drm_gpuvm.h
index fdfc575b260360611ff8ce16c327acede787929f..0d3fc1f6cac9966a42f3bc82b0b491bfefaf5b96 100644
--- a/include/drm/drm_gpuvm.h
+++ b/include/drm/drm_gpuvm.h
@@ -736,8 +736,8 @@ drm_gpuvm_bo_create(struct drm_gpuvm *gpuvm,
 		    struct drm_gem_object *obj);
 
 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 *
 drm_gpuvm_bo_obtain_prealloc(struct drm_gpuvm_bo *vm_bo);
 

-- 
2.52.0.351.gbe84eed79e-goog