Re: [PATCH net-next v5 08/15] virtio_net: sq support premapped mode

[Jason Wang]

On Mon, Jun 17, 2024 at 1:00 PM Jason Wang <jasow...@redhat.com> wrote:
>
> On Fri, Jun 14, 2024 at 2:39 PM Xuan Zhuo <xuanz...@linux.alibaba.com> wrote:
> >
> > If the xsk is enabling, the xsk tx will share the send queue.
> > But the xsk requires that the send queue use the premapped mode.
> > So the send queue must support premapped mode when it is bound to
> > af-xdp.
> >
> > * virtnet_sq_set_premapped(sq, true) is used to enable premapped mode.
> >
> >     In this mode, the driver will record the dma info when skb or xdp
> >     frame is sent.
> >
> >     Currently, the SQ premapped mode is operational only with af-xdp. In
> >     this mode, af-xdp, the kernel stack, and xdp tx/redirect will share
> >     the same SQ. Af-xdp independently manages its DMA. The kernel stack
> >     and xdp tx/redirect utilize this DMA metadata to manage the DMA
> >     info.
> >

Note that there's indeed a mode when we have exclusive XDP TX queue:

        /* XDP requires extra queues for XDP_TX */
        if (curr_qp + xdp_qp > vi->max_queue_pairs) {
                netdev_warn_once(dev, "XDP request %i queues but max
is %i. XDP_TX and XDP_REDIRECT will operate in a slower locked tx
mode.\n",
                                 curr_qp + xdp_qp, vi->max_queue_pairs);
                xdp_qp = 0;
        }

So we need to mention how the code works in this patch.

Thanks