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Message-ID: <20230216141856.fnczv3ui6d3lpujy@sgarzare-redhat> Date: Thu, 16 Feb 2023 15:18:56 +0100 From: Stefano Garzarella <sgarzare@...hat.com> To: Arseniy Krasnov <AVKrasnov@...rdevices.ru> Cc: Stefan Hajnoczi <stefanha@...hat.com>, "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Krasnov Arseniy <oxffffaa@...il.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>, "virtualization@...ts.linux-foundation.org" <virtualization@...ts.linux-foundation.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, kernel <kernel@...rdevices.ru> Subject: Re: [RFC PATCH v1 05/12] vsock/virtio: non-linear skb support On Mon, Feb 06, 2023 at 06:58:24AM +0000, Arseniy Krasnov wrote: >Use pages of non-linear skb as buffers in virtio tx queue. > >Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru> >--- > net/vmw_vsock/virtio_transport.c | 31 +++++++++++++++++++++++++------ > 1 file changed, 25 insertions(+), 6 deletions(-) > >diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c >index 28b5a8e8e094..b8a7d6dc9f46 100644 >--- a/net/vmw_vsock/virtio_transport.c >+++ b/net/vmw_vsock/virtio_transport.c >@@ -100,7 +100,8 @@ virtio_transport_send_pkt_work(struct work_struct *work) > vq = vsock->vqs[VSOCK_VQ_TX]; > > for (;;) { >- struct scatterlist hdr, buf, *sgs[2]; >+ struct scatterlist *sgs[MAX_SKB_FRAGS + 1]; >+ struct scatterlist bufs[MAX_SKB_FRAGS + 1]; + 1 is for the header, right? I'd add a comment just to be clear ;-) > int ret, in_sg = 0, out_sg = 0; > struct sk_buff *skb; > bool reply; >@@ -111,12 +112,30 @@ 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]; >+ >+ if (skb_is_nonlinear(skb)) { >+ int i; >+ >+ for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) { >+ struct page *data_page = skb_shinfo(skb)->frags[i].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. >+ */ IIUC data_page is a user page, so since we are exposing it to the host, I think we should pin it. Is data_page always a user page, or can it be a kernel page when skb is nonlinear? Thanks, Stefano >+ sg_init_one(&bufs[i + 1], >+ page_to_virt(data_page), PAGE_SIZE); >+ sgs[out_sg++] = &bufs[i + 1]; >+ } >+ } else { >+ if (skb->len > 0) { >+ sg_init_one(&bufs[1], skb->data, skb->len); >+ sgs[out_sg++] = &bufs[1]; >+ } > >- 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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