On Tue, Mar 5, 2024, at 03:01, Mina Almasry wrote:
> +int netdev_bind_dmabuf(struct net_device *dev, unsigned int dmabuf_fd,
> + struct netdev_dmabuf_binding **out)
> +{
> + struct netdev_dmabuf_binding *binding;
> + static u32 id_alloc_next;
> + struct scatterlist *sg;
> + struct dma_buf *dmabuf;
> + unsigned int sg_idx, i;
> + unsigned long virtual;
> + int err;
> +
> + if (!capable(CAP_NET_ADMIN))
> + return -EPERM;
> +
> + dmabuf = dma_buf_get(dmabuf_fd);
> + if (IS_ERR_OR_NULL(dmabuf))
> + return -EBADFD;
You should never need to use IS_ERR_OR_NULL() for a properly
defined kernel interface. This one should always return an
error or a valid pointer, so don't check for NULL.
> + binding->attachment = dma_buf_attach(binding->dmabuf, dev->dev.parent);
> + if (IS_ERR(binding->attachment)) {
> + err = PTR_ERR(binding->attachment);
> + goto err_free_id;
> + }
> +
> + binding->sgt =
> + dma_buf_map_attachment(binding->attachment, DMA_BIDIRECTIONAL);
> + if (IS_ERR(binding->sgt)) {
> + err = PTR_ERR(binding->sgt);
> + goto err_detach;
> + }
Should there be a check to verify that this buffer
is suitable for network data?
In general, dmabuf allows buffers that are uncached or reside
in MMIO space of another device, but I think this would break
when you get an skb with those buffers and try to parse the
data inside of the kernel on architectures where MMIO space
is not a normal pointer or unaligned access is disallowed on
uncached data.
Arnd
