On Tue, 5 Nov 2024 11:23:50 +0800, Jason Wang [off-list ref] wrote:

On Wed, Oct 30, 2024 at 4:25 PM Xuan Zhuo [off-list ref] wrote:

quoted

virtio-net rq submits premapped per-buffer by setting sg page to NULL;

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
 drivers/net/virtio_net.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 792e9eadbfc3..09757fa408bd 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -542,6 +542,12 @@ static struct sk_buff *ptr_to_skb(void *ptr)
        return (struct sk_buff *)((unsigned long)ptr & ~VIRTIO_ORPHAN_FLAG);
 }

+static void sg_fill_dma(struct scatterlist *sg, dma_addr_t addr, u32 len)
+{
+       sg->dma_address = addr;
+       sg->length = len;

This may work but I think it's better to reuse existing dma sg helpers like:

sg_dma_address(sg) = addr;
sg_dma_length(sg) = len;

And we probably need to fix the virtio core which only uses
sg_dma_address() but not sg_dma_length().

This helps us to avoid future issues when CONFIG_NEED_SG_DMA_LENGTH is set.

I don't think so.

For no-premapped mode, we pass the sg as no-dma sg to virtio core,
so the virtio core uses the sg->length directly.
If virtio core do dma map for sg, we do not use the dma_mag_sg_attrs(),
so we must use sg->length directly.

In this case, for the driver, we can not use sg_dma_length(),
if CONFIG_NEED_SG_DMA_LENGTH is set, sg_dma_length() will set sg->dma_length,
but virtio core use sg->length.

For sg->dma_address, it is ok for me to use sg_dma_address or not.
But for consistency to sg->length, I use the sg->dma_address directly.

I noticed this is special, so I put them into an independent function.

Thanks.

Others look good.

Thanks

quoted

+}
+
 static void __free_old_xmit(struct send_queue *sq, struct netdev_queue *txq,
                            bool in_napi, struct virtnet_sq_free_stats *stats)
 {

@@ -915,8 +921,7 @@ static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 len)
        addr = dma->addr - sizeof(*dma) + offset;

        sg_init_table(rq->sg, 1);
-       rq->sg[0].dma_address = addr;
-       rq->sg[0].length = len;
+       sg_fill_dma(rq->sg, addr, len);
 }

 static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp)

@@ -1068,12 +1073,6 @@ static void check_sq_full_and_disable(struct virtnet_info *vi,
        }
 }

-static void sg_fill_dma(struct scatterlist *sg, dma_addr_t addr, u32 len)
-{
-       sg->dma_address = addr;
-       sg->length = len;
-}
-
 static struct xdp_buff *buf_to_xdp(struct virtnet_info *vi,
                                   struct receive_queue *rq, void *buf, u32 len)
 {

@@ -1354,7 +1353,8 @@ static int virtnet_add_recvbuf_xsk(struct virtnet_info *vi, struct receive_queue
                sg_init_table(rq->sg, 1);
                sg_fill_dma(rq->sg, addr, len);

-               err = virtqueue_add_inbuf(rq->vq, rq->sg, 1, xsk_buffs[i], gfp);
+               err = virtqueue_add_inbuf_premapped(rq->vq, rq->sg, 1, xsk_buffs[i],
+                                                   NULL, true, gfp);
                if (err)
                        goto err;
        }

@@ -2431,7 +2431,8 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,

        virtnet_rq_init_one_sg(rq, buf, vi->hdr_len + GOOD_PACKET_LEN);

-       err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp);
+       err = virtqueue_add_inbuf_premapped(rq->vq, rq->sg, 1, buf, ctx,
+                                           rq->do_dma, gfp);
        if (err < 0) {
                if (rq->do_dma)
                        virtnet_rq_unmap(rq, buf, 0);

@@ -2546,7 +2547,8 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
        virtnet_rq_init_one_sg(rq, buf, len);

        ctx = mergeable_len_to_ctx(len + room, headroom);
-       err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp);
+       err = virtqueue_add_inbuf_premapped(rq->vq, rq->sg, 1, buf, ctx,
+                                           rq->do_dma, gfp);
        if (err < 0) {
                if (rq->do_dma)
                        virtnet_rq_unmap(rq, buf, 0);
--

2.32.0.3.g01195cf9f