linux-kernel - Re: [PATCH net-next v3 1/2] vsock/virtio: refactor virtio_transport_send_pkt

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Message-ID: <5myg3te4nmgrddh3dvh6t4guvmr4i73uwksyf2g4h4n3gjqk74@mf43vrv5gym2>
Date: Fri, 12 Jul 2024 15:41:51 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: luigi.leonardi@...look.com
Cc: Stefan Hajnoczi <stefanha@...hat.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, kvm@...r.kernel.org, 
	virtualization@...ts.linux.dev, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Marco Pinna <marco.pinn95@...il.com>
Subject: Re: [PATCH net-next v3 1/2] vsock/virtio: refactor
 virtio_transport_send_pkt_work

On Thu, Jul 11, 2024 at 04:58:46PM GMT, Luigi Leonardi via B4 Relay wrote:
>From: Marco Pinna <marco.pinn95@...il.com>
>
>Preliminary patch to introduce an optimization to the
>enqueue system.
>
>All the code used to enqueue a packet into the virtqueue
>is removed from virtio_transport_send_pkt_work()
>and moved to the new virtio_transport_send_skb() function.
>
>Co-developed-by: Luigi Leonardi <luigi.leonardi@...look.com>
>Signed-off-by: Luigi Leonardi <luigi.leonardi@...look.com>
>Signed-off-by: Marco Pinna <marco.pinn95@...il.com>
>---
> net/vmw_vsock/virtio_transport.c | 105 ++++++++++++++++++++++-----------------
> 1 file changed, 59 insertions(+), 46 deletions(-)

LGTM

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

>
>diff --git a/net/vmw_vsock/virtio_transport.c 
>b/net/vmw_vsock/virtio_transport.c
>index 43d405298857..c4205c22f40b 100644
>--- a/net/vmw_vsock/virtio_transport.c
>+++ b/net/vmw_vsock/virtio_transport.c
>@@ -94,6 +94,63 @@ static u32 virtio_transport_get_local_cid(void)
> 	return ret;
> }
>
>+/* Caller need to hold vsock->tx_lock on vq */
>+static int virtio_transport_send_skb(struct sk_buff *skb, struct virtqueue *vq,
>+				     struct virtio_vsock *vsock)
>+{
>+	int ret, in_sg = 0, out_sg = 0;
>+	struct scatterlist **sgs;
>+
>+	sgs = vsock->out_sgs;
>+	sg_init_one(sgs[out_sg], virtio_vsock_hdr(skb),
>+		    sizeof(*virtio_vsock_hdr(skb)));
>+	out_sg++;
>+
>+	if (!skb_is_nonlinear(skb)) {
>+		if (skb->len > 0) {
>+			sg_init_one(sgs[out_sg], skb->data, skb->len);
>+			out_sg++;
>+		}
>+	} else {
>+		struct skb_shared_info *si;
>+		int i;
>+
>+		/* If skb is nonlinear, then its buffer must contain
>+		 * only header and nothing more. Data is stored in
>+		 * the fragged part.
>+		 */
>+		WARN_ON_ONCE(skb_headroom(skb) != sizeof(*virtio_vsock_hdr(skb)));
>+
>+		si = skb_shinfo(skb);
>+
>+		for (i = 0; i < si->nr_frags; i++) {
>+			skb_frag_t *skb_frag = &si->frags[i];
>+			void *va;
>+
>+			/* We will use 'page_to_virt()' for the userspace page
>+			 * here, because virtio or dma-mapping layers will call
>+			 * 'virt_to_phys()' later to fill the buffer descriptor.
>+			 * We don't touch memory at "virtual" address of this page.
>+			 */
>+			va = page_to_virt(skb_frag_page(skb_frag));
>+			sg_init_one(sgs[out_sg],
>+				    va + skb_frag_off(skb_frag),
>+				    skb_frag_size(skb_frag));
>+			out_sg++;
>+		}
>+	}
>+
>+	ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, GFP_KERNEL);
>+	/* Usually this means that there is no more space available in
>+	 * the vq
>+	 */
>+	if (ret < 0)
>+		return ret;
>+
>+	virtio_transport_deliver_tap_pkt(skb);
>+	return 0;
>+}
>+
> static void
> virtio_transport_send_pkt_work(struct work_struct *work)
> {
>@@ -111,66 +168,22 @@ virtio_transport_send_pkt_work(struct work_struct *work)
> 	vq = vsock->vqs[VSOCK_VQ_TX];
>
> 	for (;;) {
>-		int ret, in_sg = 0, out_sg = 0;
>-		struct scatterlist **sgs;
> 		struct sk_buff *skb;
> 		bool reply;
>+		int ret;
>
> 		skb = virtio_vsock_skb_dequeue(&vsock->send_pkt_queue);
> 		if (!skb)
> 			break;
>
> 		reply = virtio_vsock_skb_reply(skb);
>-		sgs = vsock->out_sgs;
>-		sg_init_one(sgs[out_sg], virtio_vsock_hdr(skb),
>-			    sizeof(*virtio_vsock_hdr(skb)));
>-		out_sg++;
>-
>-		if (!skb_is_nonlinear(skb)) {
>-			if (skb->len > 0) {
>-				sg_init_one(sgs[out_sg], skb->data, skb->len);
>-				out_sg++;
>-			}
>-		} else {
>-			struct skb_shared_info *si;
>-			int i;
>-
>-			/* If skb is nonlinear, then its buffer must contain
>-			 * only header and nothing more. Data is stored in
>-			 * the fragged part.
>-			 */
>-			WARN_ON_ONCE(skb_headroom(skb) != sizeof(*virtio_vsock_hdr(skb)));
>-
>-			si = skb_shinfo(skb);
>
>-			for (i = 0; i < si->nr_frags; i++) {
>-				skb_frag_t *skb_frag = &si->frags[i];
>-				void *va;
>-
>-				/* We will use 'page_to_virt()' for the userspace page
>-				 * here, because virtio or dma-mapping layers will call
>-				 * 'virt_to_phys()' later to fill the buffer descriptor.
>-				 * We don't touch memory at "virtual" address of this page.
>-				 */
>-				va = page_to_virt(skb_frag_page(skb_frag));
>-				sg_init_one(sgs[out_sg],
>-					    va + skb_frag_off(skb_frag),
>-					    skb_frag_size(skb_frag));
>-				out_sg++;
>-			}
>-		}
>-
>-		ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, GFP_KERNEL);
>-		/* Usually this means that there is no more space available in
>-		 * the vq
>-		 */
>+		ret = virtio_transport_send_skb(skb, vq, vsock);
> 		if (ret < 0) {
> 			virtio_vsock_skb_queue_head(&vsock->send_pkt_queue, skb);
> 			break;
> 		}
>
>-		virtio_transport_deliver_tap_pkt(skb);
>-
> 		if (reply) {
> 			struct virtqueue *rx_vq = vsock->vqs[VSOCK_VQ_RX];
> 			int val;
>
>-- 
>2.45.2
>
>