On Fri, 20 Oct 2023 14:50:52 +0800, Jason Wang [off-list ref] wrote:

On Mon, Oct 16, 2023 at 8:01 PM Xuan Zhuo [off-list ref] wrote:

quoted

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.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
 drivers/net/virtio/main.c       | 108 ++++++++++++++++++++++++++++----
 drivers/net/virtio/virtio_net.h |  54 +++++++++++++++-
 2 files changed, 149 insertions(+), 13 deletions(-)

diff --git a/drivers/net/virtio/main.c b/drivers/net/virtio/main.c
index 8da84ea9bcbe..02d27101fef1 100644
--- a/drivers/net/virtio/main.c
+++ b/drivers/net/virtio/main.c

@@ -514,20 +514,104 @@ static void *virtnet_rq_alloc(struct virtnet_rq *rq, u32 size, gfp_t gfp)
        return buf;
 }

-static void virtnet_rq_set_premapped(struct virtnet_info *vi)
+static int virtnet_sq_set_premapped(struct virtnet_sq *sq)
 {
-       int i;
+       struct virtnet_sq_dma *d;
+       int err, size, i;

-       /* disable for big mode */
-       if (!vi->mergeable_rx_bufs && vi->big_packets)
-               return;

Not specific to this patch but any plan to fix the big mode?

For big, we should make it support XDP and do dma first.

quoted

+       size = virtqueue_get_vring_size(sq->vq);
+
+       size += MAX_SKB_FRAGS + 2;
+
+       sq->dmainfo.head = kcalloc(size, sizeof(*sq->dmainfo.head), GFP_KERNEL);
+       if (!sq->dmainfo.head)
+               return -ENOMEM;
+
+       err = virtqueue_set_dma_premapped(sq->vq);
+       if (err) {
+               kfree(sq->dmainfo.head);
+               return err;
+       }
+
+       sq->dmainfo.free = NULL;
+

[...]

quoted

+
+               d->addr = sg->dma_address;
+               d->len = sg->length;
+
+               d->next = head;
+               head = d;

It's really a pity that we need to duplicate those DMA metata twice.
Could we invent a new API to just fetch it from the virtio core?

Actually, I posted that patch.

Consider this is pushing to net-next. We can do that on top.

quoted

+       }
+
+       head->data = data;
+
+       return (void *)((unsigned long)head | ((unsigned long)data & VIRTIO_XMIT_DATA_MASK));

If we packed everything into dmainfo, we can leave the type (XDP vs
skb) there to avoid trick like packing it into the pointer here?

Yes. But if the virtio has not _ACCESS_PLATFORM, the driver will
has not the DMA meta data.

Thanks.

Thanks