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SubjectRe: [RFC PATCH v5 03/17] vsock/virtio: support to send non-linear skb
On Sat, Jul 01, 2023 at 09:39:33AM +0300, Arseniy Krasnov wrote:
>For non-linear skb use its pages from fragment array as buffers in
>virtio tx queue. These pages are already pinned by 'get_user_pages()'
>during such skb creation.
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> Changelog:
> v4 -> v5:
> * Use 'out_sgs' variable to index 'bufs', not only 'sgs'.
> * Move smaller branch above, see 'if (!skb_is_nonlinear(skb)').
> * Remove blank line.
> * R-b from Bobby Eshleman removed due to patch update.
>
> net/vmw_vsock/virtio_transport.c | 40 +++++++++++++++++++++++++++-----
> 1 file changed, 34 insertions(+), 6 deletions(-)

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

>
>diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>index e95df847176b..6cbb45bb12d2 100644
>--- a/net/vmw_vsock/virtio_transport.c
>+++ b/net/vmw_vsock/virtio_transport.c
>@@ -100,7 +100,9 @@ virtio_transport_send_pkt_work(struct work_struct *work)
> vq = vsock->vqs[VSOCK_VQ_TX];
>
> for (;;) {
>- struct scatterlist hdr, buf, *sgs[2];
>+ /* +1 is for packet header. */
>+ struct scatterlist *sgs[MAX_SKB_FRAGS + 1];
>+ struct scatterlist bufs[MAX_SKB_FRAGS + 1];
> int ret, in_sg = 0, out_sg = 0;
> struct sk_buff *skb;
> bool reply;
>@@ -111,12 +113,38 @@ virtio_transport_send_pkt_work(struct work_struct *work)
>
> virtio_transport_deliver_tap_pkt(skb);
> reply = virtio_vsock_skb_reply(skb);
>+ sg_init_one(&bufs[out_sg], virtio_vsock_hdr(skb),
>+ sizeof(*virtio_vsock_hdr(skb)));
>+ sgs[out_sg] = &bufs[out_sg];
>+ out_sg++;
>+
>+ if (!skb_is_nonlinear(skb)) {
>+ if (skb->len > 0) {
>+ sg_init_one(&bufs[out_sg], skb->data, skb->len);
>+ sgs[out_sg] = &bufs[out_sg];
>+ out_sg++;
>+ }
>+ } else {
>+ struct skb_shared_info *si;
>+ int i;
>+
>+ si = skb_shinfo(skb);
>+
>+ for (i = 0; i < si->nr_frags; i++) {
>+ skb_frag_t *skb_frag = &si->frags[i];
>+ void *va = page_to_virt(skb_frag->bv_page);
>
>- sg_init_one(&hdr, virtio_vsock_hdr(skb), sizeof(*virtio_vsock_hdr(skb)));
>- sgs[out_sg++] = &hdr;
>- if (skb->len > 0) {
>- sg_init_one(&buf, skb->data, skb->len);
>- sgs[out_sg++] = &buf;
>+ /* We will use 'page_to_virt()' for userspace page here,
>+ * because virtio layer will call 'virt_to_phys()' later
>+ * to fill buffer descriptor. We don't touch memory at
>+ * "virtual" address of this page.
>+ */
>+ sg_init_one(&bufs[out_sg],
>+ va + skb_frag->bv_offset,
>+ skb_frag->bv_len);
>+ sgs[out_sg] = &bufs[out_sg];
>+ out_sg++;
>+ }
> }
>
> ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, GFP_KERNEL);
>--
>2.25.1
>

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