Messages in this thread | | | Date | Tue, 27 Jun 2023 09:49:01 +0200 | From | Stefano Garzarella <> | Subject | Re: [RFC PATCH v4 03/17] vsock/virtio: support to send non-linear skb |
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On Tue, Jun 27, 2023 at 07:39:41AM +0300, Arseniy Krasnov wrote: > > >On 26.06.2023 18:36, Stefano Garzarella wrote: >> On Sat, Jun 03, 2023 at 11:49:25PM +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> >>> --- >>> net/vmw_vsock/virtio_transport.c | 37 ++++++++++++++++++++++++++------ >>> 1 file changed, 31 insertions(+), 6 deletions(-) >>> >>> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c >>> index e95df847176b..6053d8341091 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 +113,35 @@ 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[0], virtio_vsock_hdr(skb), sizeof(*virtio_vsock_hdr(skb))); >>> + sgs[out_sg++] = &bufs[0]; >> >> Can we use out_sg also to index bufs (here and in the rest of the code)? >> >> E.g. >> >> sg_init_one(&bufs[out_sg], ...) >> sgs[out_sg] = &bufs[out_sg]; >> ++out_sg; >> >> ... >> if (skb->len > 0) { >> sg_init_one(&bufs[out_sg], skb->data, skb->len); >> sgs[out_sg] = &bufs[out_sg]; >> ++out_sg; >> } >> >> etc... >> >>> + >> >> For readability, I would move the smaller branch above: >> >> if (!skb_is_nonlinear(skb)) { >> // small block >> ... >> } else { >> // big block >> ... >> } >> >>> + if (skb_is_nonlinear(skb)) { >>> + 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); >>> + >>> + /* 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[i + 1], >>> + va + skb_frag->bv_offset, >>> + skb_frag->bv_len); >>> + sgs[out_sg++] = &bufs[i + 1]; >>> + } >>> + } else { >>> + if (skb->len > 0) { >> >> Should we do the same check (skb->len > 0) for nonlinear skb as well? >> Or do the nonlinear ones necessarily have len > 0? > >Yes, non-linear skb always has 'data_len' > 0, e.g. such skbs always have some >data in it.
Okay, makes sense ;-)
Thanks, Stefano
> >Thanks, Arseniy > >> >>> + sg_init_one(&bufs[1], skb->data, skb->len); >>> + sgs[out_sg++] = &bufs[1]; >>> + } >>> >> ^ >> Blank line that we can remove. >> >> Stefano >> >>> - 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; >>> } >>> >>> ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, GFP_KERNEL); >>> -- >>> 2.25.1 >>> >> >
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