[RFC,18/24] drm/msm: Add _NO_SHARE flag

Commit Message

Rob Clark Dec. 7, 2024, 4:15 p.m. UTC

From: Rob Clark <[e-mail]>

Buffers that are not shared between contexts can share a single resv
object.  This way drm_gpuvm will not track them as external objects, and
submit-time validating overhead will be O(1) for all N non-shared BOs,
instead of O(n).

Signed-off-by: Rob Clark <[e-mail]>
---
 drivers/gpu/drm/msm/msm_drv.h       |  1 +
 drivers/gpu/drm/msm/msm_gem.c       | 23 +++++++++++++++++++++++
 drivers/gpu/drm/msm/msm_gem_prime.c | 15 +++++++++++++++
 include/uapi/drm/msm_drm.h          | 14 ++++++++++++++
 4 files changed, 53 insertions(+)

Patch

diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
index 80582c0c2bf7..4c7ff83a0a20 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -246,6 +246,7 @@  int msm_gem_prime_vmap(struct drm_gem_object *obj, struct iosys_map *map);
 void msm_gem_prime_vunmap(struct drm_gem_object *obj, struct iosys_map *map);
 struct drm_gem_object *msm_gem_prime_import_sg_table(struct drm_device *dev,
 		struct dma_buf_attachment *attach, struct sg_table *sg);
+struct dma_buf *msm_gem_prime_export(struct drm_gem_object *obj, int flags);
 int msm_gem_prime_pin(struct drm_gem_object *obj);
 void msm_gem_prime_unpin(struct drm_gem_object *obj);
 
diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 66332481c4c3..c21e1284f289 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -511,6 +511,9 @@  static int get_and_pin_iova_range_locked(struct drm_gem_object *obj,
 
 	msm_gem_assert_locked(obj);
 
+	if (to_msm_bo(obj)->flags & MSM_BO_NO_SHARE)
+		return -EINVAL;
+
 	vma = get_vma_locked(obj, vm, range_start, range_end);
 	if (IS_ERR(vma))
 		return PTR_ERR(vma);
@@ -1026,6 +1029,16 @@  static void msm_gem_free_object(struct drm_gem_object *obj)
 		put_iova_vmas(obj);
 	}
 
+	if (msm_obj->flags & MSM_BO_NO_SHARE) {
+		struct drm_gem_object *r_obj =
+			container_of(obj->resv, struct drm_gem_object, _resv);
+
+		BUG_ON(obj->resv == &obj->_resv);
+
+		/* Drop reference we hold to shared resv obj: */
+		drm_gem_object_put(r_obj);
+	}
+
 	drm_gem_object_release(obj);
 
 	kfree(msm_obj->metadata);
@@ -1058,6 +1071,15 @@  int msm_gem_new_handle(struct drm_device *dev, struct drm_file *file,
 	if (name)
 		msm_gem_object_set_name(obj, "%s", name);
 
+	if (flags & MSM_BO_NO_SHARE) {
+		struct msm_context *ctx = file->driver_priv;
+		struct drm_gem_object *r_obj = drm_gpuvm_resv_obj(ctx->vm);
+
+		drm_gem_object_get(r_obj);
+
+		obj->resv = r_obj->resv;
+	}
+
 	ret = drm_gem_handle_create(file, obj, handle);
 
 	/* drop reference from allocate - handle holds it now */
@@ -1090,6 +1112,7 @@  static const struct drm_gem_object_funcs msm_gem_object_funcs = {
 	.free = msm_gem_free_object,
 	.open = msm_gem_open,
 	.close = msm_gem_close,
+	.export = msm_gem_prime_export,
 	.pin = msm_gem_prime_pin,
 	.unpin = msm_gem_prime_unpin,
 	.get_sg_table = msm_gem_prime_get_sg_table,
diff --git a/drivers/gpu/drm/msm/msm_gem_prime.c b/drivers/gpu/drm/msm/msm_gem_prime.c
index ee267490c935..1a6d8099196a 100644
--- a/drivers/gpu/drm/msm/msm_gem_prime.c
+++ b/drivers/gpu/drm/msm/msm_gem_prime.c
@@ -16,6 +16,9 @@  struct sg_table *msm_gem_prime_get_sg_table(struct drm_gem_object *obj)
 	struct msm_gem_object *msm_obj = to_msm_bo(obj);
 	int npages = obj->size >> PAGE_SHIFT;
 
+	if (msm_obj->flags & MSM_BO_NO_SHARE)
+		return ERR_PTR(-EINVAL);
+
 	if (WARN_ON(!msm_obj->pages))  /* should have already pinned! */
 		return ERR_PTR(-ENOMEM);
 
@@ -45,6 +48,15 @@  struct drm_gem_object *msm_gem_prime_import_sg_table(struct drm_device *dev,
 	return msm_gem_import(dev, attach->dmabuf, sg);
 }
 
+
+struct dma_buf *msm_gem_prime_export(struct drm_gem_object *obj, int flags)
+{
+	if (to_msm_bo(obj)->flags & MSM_BO_NO_SHARE)
+		return ERR_PTR(-EPERM);
+
+	return drm_gem_prime_export(obj, flags);
+}
+
 int msm_gem_prime_pin(struct drm_gem_object *obj)
 {
 	struct page **pages;
@@ -53,6 +65,9 @@  int msm_gem_prime_pin(struct drm_gem_object *obj)
 	if (obj->import_attach)
 		return 0;
 
+	if (to_msm_bo(obj)->flags & MSM_BO_NO_SHARE)
+		return -EINVAL;
+
 	pages = msm_gem_pin_pages_locked(obj);
 	if (IS_ERR(pages))
 		ret = PTR_ERR(pages);
diff --git a/include/uapi/drm/msm_drm.h b/include/uapi/drm/msm_drm.h
index 39b55c8d7413..a7e48ee1dd95 100644
--- a/include/uapi/drm/msm_drm.h
+++ b/include/uapi/drm/msm_drm.h
@@ -138,6 +138,19 @@  struct drm_msm_param {
 
 #define MSM_BO_SCANOUT       0x00000001     /* scanout capable */
 #define MSM_BO_GPU_READONLY  0x00000002
+/* Private buffers do not need to be explicitly listed in the SUBMIT
+ * ioctl, unless referenced by a drm_msm_gem_submit_cmd.  Private
+ * buffers may NOT be imported/exported or used for scanout (or any
+ * other situation where buffers can be indefinitely pinned, but
+ * cases other than scanout are all kernel owned BOs which are not
+ * visible to userspace).
+ *
+ * In exchange for those constraints, all private BOs associated with
+ * a single context (drm_file) share a single dma_resv, and if there
+ * has been no eviction since the last submit, there are no per-BO
+ * bookeeping to do, significantly cutting the SUBMIT overhead.
+ */
+#define MSM_BO_NO_SHARE      0x00000004
 #define MSM_BO_CACHE_MASK    0x000f0000
 /* cache modes */
 #define MSM_BO_CACHED        0x00010000
@@ -147,6 +160,7 @@  struct drm_msm_param {
 
 #define MSM_BO_FLAGS         (MSM_BO_SCANOUT | \
                               MSM_BO_GPU_READONLY | \
+                              MSM_BO_NO_SHARE | \
                               MSM_BO_CACHE_MASK)
 
 struct drm_msm_gem_new {