Re: [PATCH] Implement a virtio GPU transport

Avi Kivity
2010-10-10T15:11:29Z

On 10/06/2010 05:59 PM, Ian Molton wrote:
> This patch implements a virtio-based transport for use by a
> virtualised OpenGL passthrough implementation.
>
> The libGL and qemu-gl code to support this patch are available here:
>
> http://gitorious.org/vm-gl-accel/qemu-gl
> http://gitorious.org/vm-gl-accel/qemu-libgl
>
>
> Comments please!

1. copy qemu-devel an virtualization@, many virtio developers live there.

2. should start with a patch to the virtio-pci spec to document what
you're doing

> +static int put_data(struct virtio_gl_data *gldata)
> +{
> + struct scatterlist *sg, *sg_list;
> + unsigned int count, ret, o_page, i_page, sg_entries;
> + struct virtio_gl_header *header =
> + (struct virtio_gl_header *)gldata->buffer;
> +
> + ret = header->buf_size;
> +
> + o_page = (header->buf_size + PAGE_SIZE-1)>> PAGE_SHIFT;

...

> + sg_init_table(sg_list, sg_entries);
> +
> + sg = vmalloc_to_sg(sg_list, gldata->buffer, o_page);
> + sg = vmalloc_to_sg(sg, gldata->buffer, i_page);
> +
> + if (!sg) {
> + ret = -EIO;
> + goto out_free;
> + }
> +
> + /* Transfer data */
> + if (virtqueue_add_buf(vq, sg_list, o_page, i_page, (void *)1)>= 0) {
> + virtqueue_kick(vq);
> + /* Chill out until it's done with the buffer. */
> + while (!virtqueue_get_buf(vq,&count))
> + cpu_relax();
> + }
> +

This is pretty gross, and will burn lots of cpu if the hypervisor
processes the queue asynchronously.

--
error compiling committee.c: too many arguments to function