[PATCH net-next v3 5/8] virtio-net: xsk zero copy xmit support xsk unaligned mode

[Xuan Zhuo]

In xsk unaligned mode, the frame pointed to by desc may span two
consecutive pages, but not more than two pages.

Signed-off-by: Xuan Zhuo <xuanz...@linux.alibaba.com>
Reviewed-by: Dust Li <dust...@linux.alibaba.com>
---
 drivers/net/virtio_net.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index c8a317a93ef7..259fafcf6028 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2562,24 +2562,42 @@ static void virtnet_xsk_check_space(struct send_queue 
*sq)
 static int virtnet_xsk_xmit(struct send_queue *sq, struct xsk_buff_pool *pool,
                            struct xdp_desc *desc)
 {
+       u32 offset, n, i, copy, copied;
        struct virtnet_info *vi;
        struct page *page;
        void *data;
-       u32 offset;
+       int err, m;
        u64 addr;
-       int err;
 
        vi = sq->vq->vdev->priv;
        addr = desc->addr;
+
        data = xsk_buff_raw_get_data(pool, addr);
+
        offset = offset_in_page(data);
+       m = desc->len - (PAGE_SIZE - offset);
+       /* xsk unaligned mode, desc will use two page */
+       if (m > 0)
+               n = 3;
+       else
+               n = 2;
 
-       sg_init_table(sq->sg, 2);
+       sg_init_table(sq->sg, n);
        sg_set_buf(sq->sg, &xsk_hdr, vi->hdr_len);
-       page = xsk_buff_xdp_get_page(pool, addr);
-       sg_set_page(sq->sg + 1, page, desc->len, offset);
 
-       err = virtqueue_add_outbuf(sq->vq, sq->sg, 2, NULL, GFP_ATOMIC);
+       copied = 0;
+       for (i = 1; i < n; ++i) {
+               copy = min_t(int, desc->len - copied, PAGE_SIZE - offset);
+
+               page = xsk_buff_xdp_get_page(pool, addr + copied);
+
+               sg_set_page(sq->sg + i, page, copy, offset);
+               copied += copy;
+               if (offset)
+                       offset = 0;
+       }
+
+       err = virtqueue_add_outbuf(sq->vq, sq->sg, n, NULL, GFP_ATOMIC);
        if (unlikely(err))
                sq->xsk.last_desc = *desc;
 
-- 
2.31.0