On Tue, Nov 12, 2019 at 5:56 AM Liam Girdwood <liam.r.girdwood@xxxxxxxxxxxxxxx> wrote: > > On Mon, 2019-11-11 at 16:54 -0800, Gurchetan Singh wrote: > > On Tue, Nov 5, 2019 at 2:55 AM Gerd Hoffmann <kraxel@xxxxxxxxxx> > > wrote: > > > Each buffer also has some properties to carry metadata, some fixed > > > (id, size, application), but > > > also allow free form (name = value, framebuffers would have > > > width/height/stride/format for example). > > > > Sounds a lot like the recently added DMA_BUF_SET_NAME ioctls: > > > > https://patchwork.freedesktop.org/patch/310349/ > > > > For virtio-wayland + virtio-vdec, the problem is sharing -- not > > allocation. > > > > Audio also needs to share buffers with firmware running on DSPs. > > > As the buffer reaches a kernel boundary, it's properties devolve into > > [fd, size]. Userspace can typically handle sharing metadata. The > > issue is the guest dma-buf fd doesn't mean anything on the host. > > > > One scenario could be: > > > > 1) Guest userspace (say, gralloc) allocates using virtio-gpu. When > > allocating, we call uuidgen() and then pass that via RESOURCE_CREATE > > hypercall to the host. > > 2) When exporting the dma-buf, we call DMA_BUF_SET_NAME (the buffer > > name will be "virtgpu-buffer-${UUID}"). > > 3) When importing, virtio-{vdec, video} reads the dma-buf name in > > userspace, and calls fd to handle. The name is sent to the host via > > a > > hypercall, giving host virtio-{vdec, video} enough information to > > identify the buffer. > > > > This solution is entirely userspace -- we can probably come up with > > something in kernel space [generate_random_uuid()] if need be. We > > only need two universal IDs: {device ID, buffer ID}. > > > > I need something where I can take a guest buffer and then convert it to > physical scatter gather page list. I can then either pass the SG page > list to the DSP firmware (for DMAC IP programming) or have the host > driver program the DMAC directly using the page list (who programs DMAC > depends on DSP architecture). So you need the HW address space from a guest allocation? Would your allocation hypercalls use something like the virtio_gpu_mem_entry (virtio_gpu.h) and the draft virtio_video_mem_entry (draft)? struct { __le64 addr; __le32 length; __le32 padding; }; /* VIRTIO_GPU_CMD_RESOURCE_ATTACH_BACKING */ struct virtio_gpu_resource_attach_backing { struct virtio_gpu_ctrl_hdr hdr; __le32 resource_id; __le32 nr_entries; *struct struct virtio_gpu_mem_entry */ }; struct virtio_video_mem_entry { __le64 addr; __le32 length; __u8 padding[4]; }; struct virtio_video_resource_attach_backing { struct virtio_video_ctrl_hdr hdr; __le32 resource_id; __le32 nr_entries; }; > > DSP FW has no access to userspace so we would need some additional API > on top of DMA_BUF_SET_NAME etc to get physical hardware pages ? The dma-buf api currently can share guest memory sg-lists. > > Liam > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: virtio-dev-unsubscribe@xxxxxxxxxxxxxxxxxxxx > For additional commands, e-mail: virtio-dev-help@xxxxxxxxxxxxxxxxxxxx >
