Re: [RFC PATCH v1 05/12] vsock/virtio: non-linear skb support
From: Stefano Garzarella <sgarzare@redhat.com>
Date: 2023-02-16 14:19:59
Also in:
kvm, lkml, virtualization
On Mon, Feb 06, 2023 at 06:58:24AM +0000, Arseniy Krasnov wrote:
quoted hunk ↗ jump to hunk
Use pages of non-linear skb as buffers in virtio tx queue. Signed-off-by: Arseniy Krasnov <redacted> --- 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 ;-)
quoted hunk ↗ jump to hunk
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