On Wed, Jul 19, 2023 at 07:46:05AM +0300, Arseniy Krasnov wrote:
On 18.07.2023 23:27, Michael S. Tsirkin wrote:
On Tue, Jul 18, 2023 at 09:02:35PM +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@xxxxxxxxxxxxxx>
Reviewed-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
---
net/vmw_vsock/virtio_transport.c | 40 +++++++++++++++++++++++++++-----
1 file changed, 34 insertions(+), 6 deletions(-)
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,
don't put comments after code they refer to, please?
+ * because virtio layer will call 'virt_to_phys()' later
it will but not always. sometimes it's the dma mapping layer.
+ * to fill buffer descriptor. We don't touch memory at
+ * "virtual" address of this page.
you need to stick "the" in a bunch of places above.
Ok, I'll fix this comment!
+ */
+ 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);
There's a problem here: if there vq is small this will fail.
So you really should check free vq s/gs and switch to non-zcopy
if too small.
Ok, so idea is that:
if (out_sg > vq->num_free)
reorganise current skb for copy mode (e.g. 2 out_sg - header and data)
and try to add it to vq again.
?
@Stefano, I'll remove net-next tag (guess RFC is not required again, but not net-next
anyway) as this change will require review. R-b I think should be also removed. All
other patches in this set still unchanged.
It's still a new feature so we have net-next tree as the target, right?
I think we should keep net-next. Even if patches require to be
re-reviewed, net-next indicates the tree where we want these to be merge
and for new features is the right one.
Ack for not putting RFC again and for R-b removal for this patch.
Thanks,
Stefano
