drm/gpuvm: add common dma-resv per struct drm_gpuvm

Provide a common dma-resv for GEM objects not being used outside of this
GPU-VM. This is used in a subsequent patch to generalize dma-resv,
external and evicted object handling and GEM validation.

Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231108001259.15123-6-dakr@redhat.com

1 files changed, 53 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_gpuvm.c b/drivers/gpu/drm/drm_gpuvm.c
index 2669f9bbc377..af5805e4d7c9 100644
--- a/drivers/gpu/drm/drm_gpuvm.c
+++ b/drivers/gpu/drm/drm_gpuvm.c
@@ -61,6 +61,15 @@
  * contained within struct drm_gpuva already. Hence, for inserting &drm_gpuva
  * entries from within dma-fence signalling critical sections it is enough to
  * pre-allocate the &drm_gpuva structures.
+ *
+ * &drm_gem_objects which are private to a single VM can share a common
+ * &dma_resv in order to improve locking efficiency (e.g. with &drm_exec).
+ * For this purpose drivers must pass a &drm_gem_object to drm_gpuvm_init(), in
+ * the following called 'resv object', which serves as the container of the
+ * GPUVM's shared &dma_resv. This resv object can be a driver specific
+ * &drm_gem_object, such as the &drm_gem_object containing the root page table,
+ * but it can also be a 'dummy' object, which can be allocated with
+ * drm_gpuvm_resv_object_alloc().
  */
 
 /**
@@ -670,11 +679,49 @@ drm_gpuvm_range_valid(struct drm_gpuvm *gpuvm,
 }
 EXPORT_SYMBOL_GPL(drm_gpuvm_range_valid);
 
+static void
+drm_gpuvm_gem_object_free(struct drm_gem_object *obj)
+{
+	drm_gem_object_release(obj);
+	kfree(obj);
+}
+
+static const struct drm_gem_object_funcs drm_gpuvm_object_funcs = {
+	.free = drm_gpuvm_gem_object_free,
+};
+
+/**
+ * drm_gpuvm_resv_object_alloc() - allocate a dummy &drm_gem_object
+ * @drm: the drivers &drm_device
+ *
+ * Allocates a dummy &drm_gem_object which can be passed to drm_gpuvm_init() in
+ * order to serve as root GEM object providing the &drm_resv shared across
+ * &drm_gem_objects local to a single GPUVM.
+ *
+ * Returns: the &drm_gem_object on success, NULL on failure
+ */
+struct drm_gem_object *
+drm_gpuvm_resv_object_alloc(struct drm_device *drm)
+{
+	struct drm_gem_object *obj;
+
+	obj = kzalloc(sizeof(*obj), GFP_KERNEL);
+	if (!obj)
+		return NULL;
+
+	obj->funcs = &drm_gpuvm_object_funcs;
+	drm_gem_private_object_init(drm, obj, 0);
+
+	return obj;
+}
+EXPORT_SYMBOL_GPL(drm_gpuvm_resv_object_alloc);
+
 /**
  * drm_gpuvm_init() - initialize a &drm_gpuvm
  * @gpuvm: pointer to the &drm_gpuvm to initialize
  * @name: the name of the GPU VA space
  * @drm: the &drm_device this VM resides in
+ * @r_obj: the resv &drm_gem_object providing the GPUVM's common &dma_resv
  * @start_offset: the start offset of the GPU VA space
  * @range: the size of the GPU VA space
  * @reserve_offset: the start of the kernel reserved GPU VA area
@@ -689,6 +736,7 @@ EXPORT_SYMBOL_GPL(drm_gpuvm_range_valid);
 void
 drm_gpuvm_init(struct drm_gpuvm *gpuvm, const char *name,
 	       struct drm_device *drm,
+	       struct drm_gem_object *r_obj,
 	       u64 start_offset, u64 range,
 	       u64 reserve_offset, u64 reserve_range,
 	       const struct drm_gpuvm_ops *ops)
@@ -699,6 +747,9 @@ drm_gpuvm_init(struct drm_gpuvm *gpuvm, const char *name,
 	gpuvm->name = name ? name : "unknown";
 	gpuvm->ops = ops;
 	gpuvm->drm = drm;
+	gpuvm->r_obj = r_obj;
+
+	drm_gem_object_get(r_obj);
 
 	drm_gpuvm_warn_check_overflow(gpuvm, start_offset, range);
 	gpuvm->mm_start = start_offset;
@@ -733,6 +784,8 @@ drm_gpuvm_destroy(struct drm_gpuvm *gpuvm)
 
 	drm_WARN(gpuvm->drm, !RB_EMPTY_ROOT(&gpuvm->rb.tree.rb_root),
 		 "GPUVA tree is not empty, potentially leaking memory.\n");
+
+	drm_gem_object_put(gpuvm->r_obj);
 }
 EXPORT_SYMBOL_GPL(drm_gpuvm_destroy);