Re: [PATCH 1/2] drm/virtio: Defer the host dumb buffer creation

[Jocelyn Falempe]

On 23/08/2024 09:04, Gerd Hoffmann wrote:
+static void virtio_gpu_deferred_create(struct virtio_gpu_object *bo,
+                                      struct virtio_gpu_device *vgdev,
+                                      const struct drm_mode_fb_cmd2 *mode_cmd)
+{
+       struct virtio_gpu_object_params params = { 0 };
+
+       params.format = virtio_gpu_translate_format(mode_cmd->pixel_format);
+       params.width = mode_cmd->width;
+       params.height = mode_cmd->height;
+       params.size = params.height * params.width * 4;
+       params.size = ALIGN(params.size, PAGE_SIZE);
+       params.dumb = true;

I'd suggest to simply store the complete virtio_gpu_object_params struct
in virtio_gpu_object instead of re-creating it here.

The struct params is much bigger than the struct virtio_gpu_object, so I 
though it would waste too much memory. Using a pointer would add an 
alloc/free pair, and a potential source of memleak. And as we have the 
required parameters in struct drm_mode_fb_cmd2, I found it better this way.


diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h 
b/drivers/gpu/drm/virtio/virtgpu_drv.h
index 64c236169db88..8d1e8dcfa8c15 100644
--- a/drivers/gpu/drm/virtio/virtgpu_drv.h
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
@@ -93,6 +93,9 @@ struct virtio_gpu_object {
        bool dumb;
        bool created;
        bool host3d_blob, guest_blob;
+       bool deferred;
+       struct virtio_gpu_mem_entry *ents;
+       unsigned int nents;
        uint32_t blob_mem, blob_flags;

Put them into a new block separated by newline, add a comment saying
those are needed for virtio_gpu_deferred_create?
Yes, I will do that in v2


@@ -229,9 +231,14 @@ int virtio_gpu_object_create(struct virtio_gpu_device 
*vgdev,
                                                  objs, fence);
                virtio_gpu_object_attach(vgdev, bo, ents, nents);
        } else {
-               virtio_gpu_cmd_create_resource(vgdev, bo, params,
-                                              objs, fence);
-               virtio_gpu_object_attach(vgdev, bo, ents, nents);
+               /* Fence is used only with blob or virgl */
+               WARN_ONCE(fence != NULL, "deferred doesn't support fence\n");

Additionally check for param->dumb to take the deferred code path?  That
should make sure there is no fence.

I think I can also duplicate virtio_gpu_object_create(), and have one 
version only for deferred dumb buffer. I will see if that doesn't make 
too much code duplication.


take care,
   Gerd


Thanks for the review,

--

Jocelyn