Re: [PATCH] drm/virtio: Create Dumb BOs as guest Blobs (v2)

On Tue, Apr 6, 2021 at 1:47 PM Vivek Kasireddy vivek.kasireddy@intel.com wrote:

If support for Blob resources is available, then dumb BOs created by the driver can be considered as guest Blobs.

v2: Don't skip transfer and flush commands as part of plane update as the device may have created a shared mapping. (Gerd)

Cc: Gerd Hoffmann kraxel@redhat.com Signed-off-by: Vivek Kasireddy vivek.kasireddy@intel.com

---

drivers/gpu/drm/virtio/virtgpu_gem.c | 8 ++++++++ drivers/gpu/drm/virtio/virtgpu_object.c | 3 +++ 2 files changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/virtio/virtgpu_gem.c b/drivers/gpu/drm/virtio/virtgpu_gem.c index 8502400b2f9c..5f49fb1cce65 100644 --- a/drivers/gpu/drm/virtio/virtgpu_gem.c +++ b/drivers/gpu/drm/virtio/virtgpu_gem.c @@ -64,6 +64,7 @@ int virtio_gpu_mode_dumb_create(struct drm_file *file_priv, { struct drm_gem_object *gobj; struct virtio_gpu_object_params params = { 0 };

•   struct virtio_gpu_device *vgdev = dev->dev_private;
    int ret;
    uint32_t pitch;
  
  

@@ -79,6 +80,13 @@ int virtio_gpu_mode_dumb_create(struct drm_file *file_priv, params.height = args->height; params.size = args->size; params.dumb = true;

•   if (vgdev->has_resource_blob) {
  

•           params.blob_mem = VIRTGPU_BLOB_MEM_GUEST;
  

•           params.blob_flags = VIRTGPU_BLOB_FLAG_USE_SHAREABLE;
  
  

This creates some log spam with crosvm + virgl_3d + vanilla linux, since transfers don't work for guest blobs. Two options:

a) Add vgdev->has_virgl_3d check and don't create a guest blob in that case. b) The interactions between TRANSFER_TO_HOST_2D and VIRTGPU_BLOB_MEM_GUEST are a bit under-defined in the spec. Though since you don't have a host side resource, you can safely skip the transfer and crosvm can be modified to do the right thing in case of RESOURCE_FLUSH.

It makes a ton of sense to have a explicit udmabuf-like flag ("BLOB_FLAG_CREATE_GUEST_HANDLE" or "BLOB_FLAG_HANDLE_FROM_GUEST" -- want to host OS agnostic -- any other ideas?), especially with 3d mode. For now, implicit udmabuf + dumb should be fine since the QEMU patches have been floating around for a while and should land soon for future use cases.

•           params.blob = true;
  

•   }
  
  

•   ret = virtio_gpu_gem_create(file_priv, dev, &params, &gobj,
                                &args->handle);
    if (ret)
  

diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c index 4ff1ec28e630..f648b0e24447 100644 --- a/drivers/gpu/drm/virtio/virtgpu_object.c +++ b/drivers/gpu/drm/virtio/virtgpu_object.c @@ -254,6 +254,9 @@ int virtio_gpu_object_create(struct virtio_gpu_device *vgdev, }

    if (params->blob) {

•           if (params->blob_mem == VIRTGPU_BLOB_MEM_GUEST)
  

•                   bo->guest_blob = true;
  

•           virtio_gpu_cmd_resource_create_blob(vgdev, bo, params,
                                                ents, nents);
    } else if (params->virgl) {
  

-- 2.26.2

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