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Jason Wang

2017-Jul-19 08:54 UTC

[PATCH net-next V2 0/5] Refine virtio-net XDP

Hi:

This series brings two optimizations for virtio-net XDP:

- avoid reset during XDP set
- turn off offloads on demand

Changes from V1:
- Various tweaks on commit logs and comments
- Use virtnet_napi_enable() when enabling NAPI on XDP set
- Copy the small buffer packet only if xdp_headroom is smaller than
  required

Please review.

Thanks

Jason Wang (5):
  virtio_ring: allow to store zero as the ctx
  virtio-net: pack headroom into ctx for mergeable buffers
  virtio-net: switch to use new ctx API for small buffer
  virtio-net: do not reset during XDP set
  virtio-net: switch off offloads on demand if possible on XDP set

 drivers/net/virtio_net.c     | 332 ++++++++++++++++++++++++++-----------------
 drivers/virtio/virtio_ring.c |   2 +-
 2 files changed, 200 insertions(+), 134 deletions(-)

-- 
2.7.4

Jason Wang

2017-Jul-19 08:54 UTC

head link

[PATCH net-next V2 1/5] virtio_ring: allow to store zero as the ctx

Allow zero to be store as a ctx, with this we could store e.g zero
value which could be meaningful for the case of storing headroom
through ctx.

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/virtio/virtio_ring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 5e1b548..9aaa177 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -391,7 +391,7 @@ static inline int virtqueue_add(struct virtqueue *_vq,
 	vq->desc_state[head].data = data;
 	if (indirect)
 		vq->desc_state[head].indir_desc = desc;
-	if (ctx)
+	else
 		vq->desc_state[head].indir_desc = ctx;
 
 	/* Put entry in available array (but don't update avail->idx until they
-- 
2.7.4

Jason Wang

2017-Jul-19 08:54 UTC

head link

[PATCH net-next V2 2/5] virtio-net: pack headroom into ctx for mergeable buffers

Pack headroom into ctx - this way when we get a buffer we can figure out
the actual headroom that was allocated for the buffer. Will be helpful
to optimize switching between XDP and non-XDP modes which have different
headroom requirements.

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/net/virtio_net.c | 29 ++++++++++++++++++++++++-----
 1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 1f8c15c..8fae9a8 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -270,6 +270,23 @@ static void skb_xmit_done(struct virtqueue *vq)
 		netif_wake_subqueue(vi->dev, vq2txq(vq));
 }
 
+#define MRG_CTX_HEADER_SHIFT 22
+static void *mergeable_len_to_ctx(unsigned int truesize,
+				  unsigned int headroom)
+{
+	return (void *)(unsigned long)((headroom << MRG_CTX_HEADER_SHIFT) |
truesize);
+}
+
+static unsigned int mergeable_ctx_to_headroom(void *mrg_ctx)
+{
+	return (unsigned long)mrg_ctx >> MRG_CTX_HEADER_SHIFT;
+}
+
+static unsigned int mergeable_ctx_to_truesize(void *mrg_ctx)
+{
+	return (unsigned long)mrg_ctx & ((1 << MRG_CTX_HEADER_SHIFT) - 1);
+}
+
 /* Called from bottom half context */
 static struct sk_buff *page_to_skb(struct virtnet_info *vi,
 				   struct receive_queue *rq,
@@ -639,13 +656,14 @@ static struct sk_buff *receive_mergeable(struct net_device
*dev,
 	}
 	rcu_read_unlock();
 
-	if (unlikely(len > (unsigned long)ctx)) {
+	truesize = mergeable_ctx_to_truesize(ctx);
+	if (unlikely(len > truesize)) {
 		pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
 			 dev->name, len, (unsigned long)ctx);
 		dev->stats.rx_length_errors++;
 		goto err_skb;
 	}
-	truesize = (unsigned long)ctx;
+
 	head_skb = page_to_skb(vi, rq, page, offset, len, truesize);
 	curr_skb = head_skb;
 
@@ -665,13 +683,14 @@ static struct sk_buff *receive_mergeable(struct net_device
*dev,
 		}
 
 		page = virt_to_head_page(buf);
-		if (unlikely(len > (unsigned long)ctx)) {
+
+		truesize = mergeable_ctx_to_truesize(ctx);
+		if (unlikely(len > truesize)) {
 			pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
 				 dev->name, len, (unsigned long)ctx);
 			dev->stats.rx_length_errors++;
 			goto err_skb;
 		}
-		truesize = (unsigned long)ctx;
 
 		num_skb_frags = skb_shinfo(curr_skb)->nr_frags;
 		if (unlikely(num_skb_frags == MAX_SKB_FRAGS)) {
@@ -889,7 +908,7 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
 
 	buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset;
 	buf += headroom; /* advance address leaving hole at front of pkt */
-	ctx = (void *)(unsigned long)len;
+	ctx = mergeable_len_to_ctx(len, headroom);
 	get_page(alloc_frag->page);
 	alloc_frag->offset += len + headroom;
 	hole = alloc_frag->size - alloc_frag->offset;
-- 
2.7.4

Jason Wang

2017-Jul-19 08:54 UTC

head link

[PATCH net-next V2 3/5] virtio-net: switch to use new ctx API for small buffer

Use ctx API to store headroom for small buffers.
Following patches will retrieve this info and use it for XDP.

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/net/virtio_net.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 8fae9a8..640f1de 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -410,7 +410,8 @@ static unsigned int virtnet_get_headroom(struct virtnet_info
*vi)
 static struct sk_buff *receive_small(struct net_device *dev,
 				     struct virtnet_info *vi,
 				     struct receive_queue *rq,
-				     void *buf, unsigned int len)
+				     void *buf, void *ctx,
+				     unsigned int len)
 {
 	struct sk_buff *skb;
 	struct bpf_prog *xdp_prog;
@@ -773,7 +774,7 @@ static int receive_buf(struct virtnet_info *vi, struct
receive_queue *rq,
 	else if (vi->big_packets)
 		skb = receive_big(dev, vi, rq, buf, len);
 	else
-		skb = receive_small(dev, vi, rq, buf, len);
+		skb = receive_small(dev, vi, rq, buf, ctx, len);
 
 	if (unlikely(!skb))
 		return 0;
@@ -806,12 +807,18 @@ static int receive_buf(struct virtnet_info *vi, struct
receive_queue *rq,
 	return 0;
 }
 
+/* Unlike mergeable buffers, all buffers are allocated to the
+ * same size, except for the headroom. For this reason we do
+ * not need to use  mergeable_len_to_ctx here - it is enough
+ * to store the headroom as the context ignoring the truesize.
+ */
 static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
 			     gfp_t gfp)
 {
 	struct page_frag *alloc_frag = &rq->alloc_frag;
 	char *buf;
 	unsigned int xdp_headroom = virtnet_get_headroom(vi);
+	void *ctx = (void *)(unsigned long)xdp_headroom;
 	int len = vi->hdr_len + VIRTNET_RX_PAD + GOOD_PACKET_LEN + xdp_headroom;
 	int err;
 
@@ -825,7 +832,7 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct
receive_queue *rq,
 	alloc_frag->offset += len;
 	sg_init_one(rq->sg, buf + VIRTNET_RX_PAD + xdp_headroom,
 		    vi->hdr_len + GOOD_PACKET_LEN);
-	err = virtqueue_add_inbuf(rq->vq, rq->sg, 1, buf, gfp);
+	err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp);
 	if (err < 0)
 		put_page(virt_to_head_page(buf));
 
@@ -1034,7 +1041,7 @@ static int virtnet_receive(struct receive_queue *rq, int
budget)
 	void *buf;
 	struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
 
-	if (vi->mergeable_rx_bufs) {
+	if (!vi->big_packets || vi->mergeable_rx_bufs) {
 		void *ctx;
 
 		while (received < budget &&
@@ -2198,7 +2205,7 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
 	names = kmalloc(total_vqs * sizeof(*names), GFP_KERNEL);
 	if (!names)
 		goto err_names;
-	if (vi->mergeable_rx_bufs) {
+	if (!vi->big_packets || vi->mergeable_rx_bufs) {
 		ctx = kzalloc(total_vqs * sizeof(*ctx), GFP_KERNEL);
 		if (!ctx)
 			goto err_ctx;
-- 
2.7.4

Jason Wang

2017-Jul-19 08:54 UTC

head link

[PATCH net-next V2 4/5] virtio-net: do not reset during XDP set

We currently reset the device during XDP set, the main reason is
that we allocate more headroom with XDP (for header adjustment).

This works but causes network downtime for users.

Previous patches encoded the headroom in the buffer context,
this makes it possible to detect the case where a buffer
with headroom insufficient for XDP is added to the queue and
XDP is enabled afterwards.

Upon detection, we handle this case by copying the packet
(slow, but it's a temporary condition).

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/net/virtio_net.c | 232 ++++++++++++++++++++++-------------------------
 1 file changed, 106 insertions(+), 126 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 640f1de..b3fc01d 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -407,6 +407,69 @@ static unsigned int virtnet_get_headroom(struct
virtnet_info *vi)
 	return vi->xdp_queue_pairs ? VIRTIO_XDP_HEADROOM : 0;
 }
 
+/* We copy the packet for XDP in the following cases:
+ *
+ * 1) Packet is scattered across multiple rx buffers.
+ * 2) Headroom space is insufficient.
+ *
+ * This is inefficient but it's a temporary condition that
+ * we hit right after XDP is enabled and until queue is refilled
+ * with large buffers with sufficient headroom - so it should affect
+ * at most queue size packets.
+ * Afterwards, the conditions to enable
+ * XDP should preclude the underlying device from sending packets
+ * across multiple buffers (num_buf > 1), and we make sure buffers
+ * have enough headroom.
+ */
+static struct page *xdp_linearize_page(struct receive_queue *rq,
+				       u16 *num_buf,
+				       struct page *p,
+				       int offset,
+				       int page_off,
+				       unsigned int *len)
+{
+	struct page *page = alloc_page(GFP_ATOMIC);
+
+	if (!page)
+		return NULL;
+
+	memcpy(page_address(page) + page_off, page_address(p) + offset, *len);
+	page_off += *len;
+
+	while (--*num_buf) {
+		unsigned int buflen;
+		void *buf;
+		int off;
+
+		buf = virtqueue_get_buf(rq->vq, &buflen);
+		if (unlikely(!buf))
+			goto err_buf;
+
+		p = virt_to_head_page(buf);
+		off = buf - page_address(p);
+
+		/* guard against a misconfigured or uncooperative backend that
+		 * is sending packet larger than the MTU.
+		 */
+		if ((page_off + buflen) > PAGE_SIZE) {
+			put_page(p);
+			goto err_buf;
+		}
+
+		memcpy(page_address(page) + page_off,
+		       page_address(p) + off, buflen);
+		page_off += buflen;
+		put_page(p);
+	}
+
+	/* Headroom does not contribute to packet length */
+	*len = page_off - VIRTIO_XDP_HEADROOM;
+	return page;
+err_buf:
+	__free_pages(page, 0);
+	return NULL;
+}
+
 static struct sk_buff *receive_small(struct net_device *dev,
 				     struct virtnet_info *vi,
 				     struct receive_queue *rq,
@@ -415,12 +478,14 @@ static struct sk_buff *receive_small(struct net_device
*dev,
 {
 	struct sk_buff *skb;
 	struct bpf_prog *xdp_prog;
-	unsigned int xdp_headroom = virtnet_get_headroom(vi);
+	unsigned int xdp_headroom = (unsigned long)ctx;
 	unsigned int header_offset = VIRTNET_RX_PAD + xdp_headroom;
 	unsigned int headroom = vi->hdr_len + header_offset;
 	unsigned int buflen = SKB_DATA_ALIGN(GOOD_PACKET_LEN + headroom) +
 			      SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+	struct page *page = virt_to_head_page(buf);
 	unsigned int delta = 0;
+	struct page *xdp_page;
 	len -= vi->hdr_len;
 
 	rcu_read_lock();
@@ -434,6 +499,27 @@ static struct sk_buff *receive_small(struct net_device
*dev,
 		if (unlikely(hdr->hdr.gso_type || hdr->hdr.flags))
 			goto err_xdp;
 
+		if (unlikely(xdp_headroom < virtnet_get_headroom(vi))) {
+			int offset = buf - page_address(page) + header_offset;
+			unsigned int tlen = len + vi->hdr_len;
+			u16 num_buf = 1;
+
+			xdp_headroom = virtnet_get_headroom(vi);
+			header_offset = VIRTNET_RX_PAD + xdp_headroom;
+			headroom = vi->hdr_len + header_offset;
+			buflen = SKB_DATA_ALIGN(GOOD_PACKET_LEN + headroom) +
+				 SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+			xdp_page = xdp_linearize_page(rq, &num_buf, page,
+						      offset, header_offset,
+						      &tlen);
+			if (!xdp_page)
+				goto err_xdp;
+
+			buf = page_address(xdp_page);
+			put_page(page);
+			page = xdp_page;
+		}
+
 		xdp.data_hard_start = buf + VIRTNET_RX_PAD + vi->hdr_len;
 		xdp.data = xdp.data_hard_start + xdp_headroom;
 		xdp.data_end = xdp.data + len;
@@ -462,7 +548,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
 
 	skb = build_skb(buf, buflen);
 	if (!skb) {
-		put_page(virt_to_head_page(buf));
+		put_page(page);
 		goto err;
 	}
 	skb_reserve(skb, headroom - delta);
@@ -478,7 +564,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
 err_xdp:
 	rcu_read_unlock();
 	dev->stats.rx_dropped++;
-	put_page(virt_to_head_page(buf));
+	put_page(page);
 xdp_xmit:
 	return NULL;
 }
@@ -503,66 +589,6 @@ static struct sk_buff *receive_big(struct net_device *dev,
 	return NULL;
 }
 
-/* The conditions to enable XDP should preclude the underlying device from
- * sending packets across multiple buffers (num_buf > 1). However per spec
- * it does not appear to be illegal to do so but rather just against
convention.
- * So in order to avoid making a system unresponsive the packets are pushed
- * into a page and the XDP program is run. This will be extremely slow and we
- * push a warning to the user to fix this as soon as possible. Fixing this may
- * require resolving the underlying hardware to determine why multiple buffers
- * are being received or simply loading the XDP program in the ingress stack
- * after the skb is built because there is no advantage to running it here
- * anymore.
- */
-static struct page *xdp_linearize_page(struct receive_queue *rq,
-				       u16 *num_buf,
-				       struct page *p,
-				       int offset,
-				       unsigned int *len)
-{
-	struct page *page = alloc_page(GFP_ATOMIC);
-	unsigned int page_off = VIRTIO_XDP_HEADROOM;
-
-	if (!page)
-		return NULL;
-
-	memcpy(page_address(page) + page_off, page_address(p) + offset, *len);
-	page_off += *len;
-
-	while (--*num_buf) {
-		unsigned int buflen;
-		void *buf;
-		int off;
-
-		buf = virtqueue_get_buf(rq->vq, &buflen);
-		if (unlikely(!buf))
-			goto err_buf;
-
-		p = virt_to_head_page(buf);
-		off = buf - page_address(p);
-
-		/* guard against a misconfigured or uncooperative backend that
-		 * is sending packet larger than the MTU.
-		 */
-		if ((page_off + buflen) > PAGE_SIZE) {
-			put_page(p);
-			goto err_buf;
-		}
-
-		memcpy(page_address(page) + page_off,
-		       page_address(p) + off, buflen);
-		page_off += buflen;
-		put_page(p);
-	}
-
-	/* Headroom does not contribute to packet length */
-	*len = page_off - VIRTIO_XDP_HEADROOM;
-	return page;
-err_buf:
-	__free_pages(page, 0);
-	return NULL;
-}
-
 static struct sk_buff *receive_mergeable(struct net_device *dev,
 					 struct virtnet_info *vi,
 					 struct receive_queue *rq,
@@ -577,6 +603,7 @@ static struct sk_buff *receive_mergeable(struct net_device
*dev,
 	struct sk_buff *head_skb, *curr_skb;
 	struct bpf_prog *xdp_prog;
 	unsigned int truesize;
+	unsigned int headroom = mergeable_ctx_to_headroom(ctx);
 
 	head_skb = NULL;
 
@@ -589,10 +616,13 @@ static struct sk_buff *receive_mergeable(struct net_device
*dev,
 		u32 act;
 
 		/* This happens when rx buffer size is underestimated */
-		if (unlikely(num_buf > 1)) {
+		if (unlikely(num_buf > 1 ||
+			     headroom < virtnet_get_headroom(vi))) {
 			/* linearize data for XDP */
 			xdp_page = xdp_linearize_page(rq, &num_buf,
-						      page, offset, &len);
+						      page, offset,
+						      VIRTIO_XDP_HEADROOM,
+						      &len);
 			if (!xdp_page)
 				goto err_xdp;
 			offset = VIRTIO_XDP_HEADROOM;
@@ -835,7 +865,6 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct
receive_queue *rq,
 	err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp);
 	if (err < 0)
 		put_page(virt_to_head_page(buf));
-
 	return err;
 }
 
@@ -1839,7 +1868,6 @@ static void virtnet_freeze_down(struct virtio_device
*vdev)
 }
 
 static int init_vqs(struct virtnet_info *vi);
-static void _remove_vq_common(struct virtnet_info *vi);
 
 static int virtnet_restore_up(struct virtio_device *vdev)
 {
@@ -1868,39 +1896,6 @@ static int virtnet_restore_up(struct virtio_device *vdev)
 	return err;
 }
 
-static int virtnet_reset(struct virtnet_info *vi, int curr_qp, int xdp_qp)
-{
-	struct virtio_device *dev = vi->vdev;
-	int ret;
-
-	virtio_config_disable(dev);
-	dev->failed = dev->config->get_status(dev) &
VIRTIO_CONFIG_S_FAILED;
-	virtnet_freeze_down(dev);
-	_remove_vq_common(vi);
-
-	virtio_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
-	virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER);
-
-	ret = virtio_finalize_features(dev);
-	if (ret)
-		goto err;
-
-	vi->xdp_queue_pairs = xdp_qp;
-	ret = virtnet_restore_up(dev);
-	if (ret)
-		goto err;
-	ret = _virtnet_set_queues(vi, curr_qp);
-	if (ret)
-		goto err;
-
-	virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
-	virtio_config_enable(dev);
-	return 0;
-err:
-	virtio_add_status(dev, VIRTIO_CONFIG_S_FAILED);
-	return ret;
-}
-
 static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
 			   struct netlink_ext_ack *extack)
 {
@@ -1947,35 +1942,29 @@ static int virtnet_xdp_set(struct net_device *dev,
struct bpf_prog *prog,
 			return PTR_ERR(prog);
 	}
 
-	/* Changing the headroom in buffers is a disruptive operation because
-	 * existing buffers must be flushed and reallocated. This will happen
-	 * when a xdp program is initially added or xdp is disabled by removing
-	 * the xdp program resulting in number of XDP queues changing.
-	 */
-	if (vi->xdp_queue_pairs != xdp_qp) {
-		err = virtnet_reset(vi, curr_qp + xdp_qp, xdp_qp);
-		if (err) {
-			dev_warn(&dev->dev, "XDP reset failure.\n");
-			goto virtio_reset_err;
-		}
-	}
+	/* Make sure NAPI is not using any XDP TX queues for RX. */
+	for (i = 0; i < vi->max_queue_pairs; i++)
+		napi_disable(&vi->rq[i].napi);
 
 	netif_set_real_num_rx_queues(dev, curr_qp + xdp_qp);
+	err = _virtnet_set_queues(vi, curr_qp + xdp_qp);
+	if (err)
+		goto err;
+	vi->xdp_queue_pairs = xdp_qp;
 
 	for (i = 0; i < vi->max_queue_pairs; i++) {
 		old_prog = rtnl_dereference(vi->rq[i].xdp_prog);
 		rcu_assign_pointer(vi->rq[i].xdp_prog, prog);
 		if (old_prog)
 			bpf_prog_put(old_prog);
+		virtnet_napi_enable(vi->rq[i].vq, &vi->rq[i].napi);
 	}
 
 	return 0;
 
-virtio_reset_err:
-	/* On reset error do our best to unwind XDP changes inflight and return
-	 * error up to user space for resolution. The underlying reset hung on
-	 * us so not much we can do here.
-	 */
+err:
+	for (i = 0; i < vi->max_queue_pairs; i++)
+		virtnet_napi_enable(vi->rq[i].vq, &vi->rq[i].napi);
 	if (prog)
 		bpf_prog_sub(prog, vi->max_queue_pairs - 1);
 	return err;
@@ -2619,15 +2608,6 @@ static int virtnet_probe(struct virtio_device *vdev)
 	return err;
 }
 
-static void _remove_vq_common(struct virtnet_info *vi)
-{
-	vi->vdev->config->reset(vi->vdev);
-	free_unused_bufs(vi);
-	_free_receive_bufs(vi);
-	free_receive_page_frags(vi);
-	virtnet_del_vqs(vi);
-}
-
 static void remove_vq_common(struct virtnet_info *vi)
 {
 	vi->vdev->config->reset(vi->vdev);
-- 
2.7.4

Jason Wang

2017-Jul-19 08:54 UTC

head link

[PATCH net-next V2 5/5] virtio-net: switch off offloads on demand if possible on XDP set

Current XDP implementation wants guest offloads feature to be disabled
on device. This is inconvenient and means guest can't benefit from
offloads if XDP is not used. This patch tries to address this
limitation by disabling the offloads on demand through control guest
offloads. Guest offloads will be disabled and enabled on demand on XDP
set.

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/net/virtio_net.c | 70 ++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 65 insertions(+), 5 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index b3fc01d..5fbd15e 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -57,6 +57,11 @@ DECLARE_EWMA(pkt_len, 0, 64)
 
 #define VIRTNET_DRIVER_VERSION "1.0.0"
 
+const unsigned long guest_offloads[] = { VIRTIO_NET_F_GUEST_TSO4,
+					 VIRTIO_NET_F_GUEST_TSO6,
+					 VIRTIO_NET_F_GUEST_ECN,
+					 VIRTIO_NET_F_GUEST_UFO };
+
 struct virtnet_stats {
 	struct u64_stats_sync tx_syncp;
 	struct u64_stats_sync rx_syncp;
@@ -164,10 +169,13 @@ struct virtnet_info {
 	u8 ctrl_promisc;
 	u8 ctrl_allmulti;
 	u16 ctrl_vid;
+	u64 ctrl_offloads;
 
 	/* Ethtool settings */
 	u8 duplex;
 	u32 speed;
+
+	unsigned long guest_offloads;
 };
 
 struct padded_vnet_hdr {
@@ -1896,6 +1904,47 @@ static int virtnet_restore_up(struct virtio_device *vdev)
 	return err;
 }
 
+static int virtnet_set_guest_offloads(struct virtnet_info *vi, u64 offloads)
+{
+	struct scatterlist sg;
+	vi->ctrl_offloads = cpu_to_virtio64(vi->vdev, offloads);
+
+	sg_init_one(&sg, &vi->ctrl_offloads, sizeof(vi->ctrl_offloads));
+
+	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_GUEST_OFFLOADS,
+				  VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET, &sg)) {
+		dev_warn(&vi->dev->dev, "Fail to set guest offload. \n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int virtnet_clear_guest_offloads(struct virtnet_info *vi)
+{
+	u64 offloads = 0;
+
+	if (!vi->guest_offloads)
+		return 0;
+
+	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
+		offloads = 1ULL << VIRTIO_NET_F_GUEST_CSUM;
+
+	return virtnet_set_guest_offloads(vi, offloads);
+}
+
+static int virtnet_restore_guest_offloads(struct virtnet_info *vi)
+{
+	u64 offloads = vi->guest_offloads;
+
+	if (!vi->guest_offloads)
+		return 0;
+	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
+		offloads |= 1ULL << VIRTIO_NET_F_GUEST_CSUM;
+
+	return virtnet_set_guest_offloads(vi, offloads);
+}
+
 static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
 			   struct netlink_ext_ack *extack)
 {
@@ -1905,10 +1954,11 @@ static int virtnet_xdp_set(struct net_device *dev,
struct bpf_prog *prog,
 	u16 xdp_qp = 0, curr_qp;
 	int i, err;
 
-	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) ||
-	    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) ||
-	    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) ||
-	    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO)) {
+	if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS)
+	    && (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) ||
+	        virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) ||
+	        virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) ||
+		virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO))) {
 		NL_SET_ERR_MSG_MOD(extack, "Can't set XDP while host is implementing
LRO, disable LRO first");
 		return -EOPNOTSUPP;
 	}
@@ -1955,6 +2005,12 @@ static int virtnet_xdp_set(struct net_device *dev, struct
bpf_prog *prog,
 	for (i = 0; i < vi->max_queue_pairs; i++) {
 		old_prog = rtnl_dereference(vi->rq[i].xdp_prog);
 		rcu_assign_pointer(vi->rq[i].xdp_prog, prog);
+		if (i == 0) {
+			if (!old_prog)
+				virtnet_clear_guest_offloads(vi);
+			if (!prog)
+				virtnet_restore_guest_offloads(vi);
+		}
 		if (old_prog)
 			bpf_prog_put(old_prog);
 		virtnet_napi_enable(vi->rq[i].vq, &vi->rq[i].napi);
@@ -2588,6 +2644,10 @@ static int virtnet_probe(struct virtio_device *vdev)
 		netif_carrier_on(dev);
 	}
 
+	for (i = 0; i < ARRAY_SIZE(guest_offloads); i++)
+		if (virtio_has_feature(vi->vdev, guest_offloads[i]))
+			set_bit(guest_offloads[i], &vi->guest_offloads);
+
 	pr_debug("virtnet: registered device %s with %d RX and TX
vq's\n",
 		 dev->name, max_queue_pairs);
 
@@ -2684,7 +2744,7 @@ static struct virtio_device_id id_table[] = {
 	VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN, \
 	VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, \
 	VIRTIO_NET_F_CTRL_MAC_ADDR, \
-	VIRTIO_NET_F_MTU
+	VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS
 
 static unsigned int features[] = {
 	VIRTNET_FEATURES,
-- 
2.7.4

David Miller

2017-Jul-24 20:38 UTC

head link

[PATCH net-next V2 0/5] Refine virtio-net XDP

From: Jason Wang <jasowang at redhat.com>
Date: Wed, 19 Jul 2017 16:54:44 +0800
> Hi:
> 
> This series brings two optimizations for virtio-net XDP:
> 
> - avoid reset during XDP set
> - turn off offloads on demand
> 
> Changes from V1:
> - Various tweaks on commit logs and comments
> - Use virtnet_napi_enable() when enabling NAPI on XDP set
> - Copy the small buffer packet only if xdp_headroom is smaller than
>   required
> 
> Please review.
Series applied, thanks Jason.

Michael, I gave you 4+ days to properly review this respin of this
series.  I felt that was more than sufficient time, even with an
intervening weekend.  So if you don't like that I applied this without
your review, please be more punctual in the future.

Thank you.

Michael S. Tsirkin

2017-Jul-24 21:29 UTC

head link

[PATCH net-next V2 5/5] virtio-net: switch off offloads on demand if possible on XDP set

On Wed, Jul 19, 2017 at 04:54:49PM +0800, Jason Wang
wrote:> Current XDP implementation wants guest offloads feature to be disabled
> on device. This is inconvenient and means guest can't benefit from
> offloads if XDP is not used. This patch tries to address this
> limitation by disabling the offloads on demand through control guest
> offloads. Guest offloads will be disabled and enabled on demand on XDP
> set.
> 
> Signed-off-by: Jason Wang <jasowang at redhat.com>
Doesn't look like my comments on v1 were addressed.
Copying here:

In fact, since we no longer reset when XDP is set,
here device might have offloads enabled, buffers are
used but not consumed, then XDP is set.

This can result in
- packet scattered across multiple buffers
  (handled correctly but need to update the comment)
- packet may have VIRTIO_NET_HDR_F_NEEDS_CSUM, in that case
  the spec says "The checksum on the packet is incomplete".
  (probably needs to be handled by calculating the checksum).

Jason, as David applied this patch already, can you comment
on the issues please?
> ---
>  drivers/net/virtio_net.c | 70
++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 65 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index b3fc01d..5fbd15e 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -57,6 +57,11 @@ DECLARE_EWMA(pkt_len, 0, 64)
>  
>  #define VIRTNET_DRIVER_VERSION "1.0.0"
>  
> +const unsigned long guest_offloads[] = { VIRTIO_NET_F_GUEST_TSO4,
> +					 VIRTIO_NET_F_GUEST_TSO6,
> +					 VIRTIO_NET_F_GUEST_ECN,
> +					 VIRTIO_NET_F_GUEST_UFO };
> +
>  struct virtnet_stats {
>  	struct u64_stats_sync tx_syncp;
>  	struct u64_stats_sync rx_syncp;
> @@ -164,10 +169,13 @@ struct virtnet_info {
>  	u8 ctrl_promisc;
>  	u8 ctrl_allmulti;
>  	u16 ctrl_vid;
> +	u64 ctrl_offloads;
>  
>  	/* Ethtool settings */
>  	u8 duplex;
>  	u32 speed;
> +
> +	unsigned long guest_offloads;
>  };
>  
>  struct padded_vnet_hdr {
> @@ -1896,6 +1904,47 @@ static int virtnet_restore_up(struct virtio_device
*vdev)
>  	return err;
>  }
>  
> +static int virtnet_set_guest_offloads(struct virtnet_info *vi, u64
offloads)
> +{
> +	struct scatterlist sg;
> +	vi->ctrl_offloads = cpu_to_virtio64(vi->vdev, offloads);
> +
> +	sg_init_one(&sg, &vi->ctrl_offloads,
sizeof(vi->ctrl_offloads));
> +
> +	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_GUEST_OFFLOADS,
> +				  VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET, &sg)) {
> +		dev_warn(&vi->dev->dev, "Fail to set guest offload.
\n");
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +static int virtnet_clear_guest_offloads(struct virtnet_info *vi)
> +{
> +	u64 offloads = 0;
> +
> +	if (!vi->guest_offloads)
> +		return 0;
> +
> +	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
> +		offloads = 1ULL << VIRTIO_NET_F_GUEST_CSUM;
> +
> +	return virtnet_set_guest_offloads(vi, offloads);
> +}
> +
> +static int virtnet_restore_guest_offloads(struct virtnet_info *vi)
> +{
> +	u64 offloads = vi->guest_offloads;
> +
> +	if (!vi->guest_offloads)
> +		return 0;
> +	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
> +		offloads |= 1ULL << VIRTIO_NET_F_GUEST_CSUM;
> +
> +	return virtnet_set_guest_offloads(vi, offloads);
> +}
> +
>  static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
>  			   struct netlink_ext_ack *extack)
>  {
> @@ -1905,10 +1954,11 @@ static int virtnet_xdp_set(struct net_device *dev,
struct bpf_prog *prog,
>  	u16 xdp_qp = 0, curr_qp;
>  	int i, err;
>  
> -	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) ||
> -	    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) ||
> -	    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) ||
> -	    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO)) {
> +	if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS)
> +	    && (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4)
||
> +	        virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) ||
> +	        virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) ||
> +		virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO))) {
>  		NL_SET_ERR_MSG_MOD(extack, "Can't set XDP while host is
implementing LRO, disable LRO first");
>  		return -EOPNOTSUPP;
>  	}
> @@ -1955,6 +2005,12 @@ static int virtnet_xdp_set(struct net_device *dev,
struct bpf_prog *prog,
>  	for (i = 0; i < vi->max_queue_pairs; i++) {
>  		old_prog = rtnl_dereference(vi->rq[i].xdp_prog);
>  		rcu_assign_pointer(vi->rq[i].xdp_prog, prog);
> +		if (i == 0) {
> +			if (!old_prog)
> +				virtnet_clear_guest_offloads(vi);
> +			if (!prog)
> +				virtnet_restore_guest_offloads(vi);
> +		}
>  		if (old_prog)
>  			bpf_prog_put(old_prog);
>  		virtnet_napi_enable(vi->rq[i].vq, &vi->rq[i].napi);
> @@ -2588,6 +2644,10 @@ static int virtnet_probe(struct virtio_device *vdev)
>  		netif_carrier_on(dev);
>  	}
>  
> +	for (i = 0; i < ARRAY_SIZE(guest_offloads); i++)
> +		if (virtio_has_feature(vi->vdev, guest_offloads[i]))
> +			set_bit(guest_offloads[i], &vi->guest_offloads);
> +
>  	pr_debug("virtnet: registered device %s with %d RX and TX
vq's\n",
>  		 dev->name, max_queue_pairs);
>  
> @@ -2684,7 +2744,7 @@ static struct virtio_device_id id_table[] = {
>  	VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN, \
>  	VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, \
>  	VIRTIO_NET_F_CTRL_MAC_ADDR, \
> -	VIRTIO_NET_F_MTU
> +	VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS
>  
>  static unsigned int features[] = {
>  	VIRTNET_FEATURES,
> -- 
> 2.7.4

Michael S. Tsirkin

2017-Jul-24 21:40 UTC

head link

[PATCH net-next V2 5/5] virtio-net: switch off offloads on demand if possible on XDP set

On Wed, Jul 19, 2017 at 04:54:49PM +0800, Jason Wang
wrote:> Current XDP implementation wants guest offloads feature to be disabled
> on device. This is inconvenient and means guest can't benefit from
> offloads if XDP is not used. This patch tries to address this
> limitation by disabling the offloads on demand through control guest
> offloads. Guest offloads will be disabled and enabled on demand on XDP
> set.
> 
> Signed-off-by: Jason Wang <jasowang at redhat.com>
Also looks like the comment from patch 4 needs to be extended
to cover LRO as cause of temporary packet scatter.
> ---
>  drivers/net/virtio_net.c | 70
++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 65 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index b3fc01d..5fbd15e 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -57,6 +57,11 @@ DECLARE_EWMA(pkt_len, 0, 64)
>  
>  #define VIRTNET_DRIVER_VERSION "1.0.0"
>  
> +const unsigned long guest_offloads[] = { VIRTIO_NET_F_GUEST_TSO4,
> +					 VIRTIO_NET_F_GUEST_TSO6,
> +					 VIRTIO_NET_F_GUEST_ECN,
> +					 VIRTIO_NET_F_GUEST_UFO };
> +
>  struct virtnet_stats {
>  	struct u64_stats_sync tx_syncp;
>  	struct u64_stats_sync rx_syncp;
> @@ -164,10 +169,13 @@ struct virtnet_info {
>  	u8 ctrl_promisc;
>  	u8 ctrl_allmulti;
>  	u16 ctrl_vid;
> +	u64 ctrl_offloads;
>  
>  	/* Ethtool settings */
>  	u8 duplex;
>  	u32 speed;
> +
> +	unsigned long guest_offloads;
>  };
>  
>  struct padded_vnet_hdr {
> @@ -1896,6 +1904,47 @@ static int virtnet_restore_up(struct virtio_device
*vdev)
>  	return err;
>  }
>  
> +static int virtnet_set_guest_offloads(struct virtnet_info *vi, u64
offloads)
> +{
> +	struct scatterlist sg;
> +	vi->ctrl_offloads = cpu_to_virtio64(vi->vdev, offloads);
> +
> +	sg_init_one(&sg, &vi->ctrl_offloads,
sizeof(vi->ctrl_offloads));
> +
> +	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_GUEST_OFFLOADS,
> +				  VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET, &sg)) {
> +		dev_warn(&vi->dev->dev, "Fail to set guest offload.
\n");
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +static int virtnet_clear_guest_offloads(struct virtnet_info *vi)
> +{
> +	u64 offloads = 0;
> +
> +	if (!vi->guest_offloads)
> +		return 0;
> +
> +	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
> +		offloads = 1ULL << VIRTIO_NET_F_GUEST_CSUM;
> +
> +	return virtnet_set_guest_offloads(vi, offloads);
> +}
> +
> +static int virtnet_restore_guest_offloads(struct virtnet_info *vi)
> +{
> +	u64 offloads = vi->guest_offloads;
> +
> +	if (!vi->guest_offloads)
> +		return 0;
> +	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
> +		offloads |= 1ULL << VIRTIO_NET_F_GUEST_CSUM;
> +
> +	return virtnet_set_guest_offloads(vi, offloads);
> +}
> +
>  static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
>  			   struct netlink_ext_ack *extack)
>  {
> @@ -1905,10 +1954,11 @@ static int virtnet_xdp_set(struct net_device *dev,
struct bpf_prog *prog,
>  	u16 xdp_qp = 0, curr_qp;
>  	int i, err;
>  
> -	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) ||
> -	    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) ||
> -	    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) ||
> -	    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO)) {
> +	if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS)
> +	    && (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4)
||
> +	        virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) ||
> +	        virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) ||
> +		virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO))) {
>  		NL_SET_ERR_MSG_MOD(extack, "Can't set XDP while host is
implementing LRO, disable LRO first");
>  		return -EOPNOTSUPP;
>  	}
> @@ -1955,6 +2005,12 @@ static int virtnet_xdp_set(struct net_device *dev,
struct bpf_prog *prog,
>  	for (i = 0; i < vi->max_queue_pairs; i++) {
>  		old_prog = rtnl_dereference(vi->rq[i].xdp_prog);
>  		rcu_assign_pointer(vi->rq[i].xdp_prog, prog);
> +		if (i == 0) {
> +			if (!old_prog)
> +				virtnet_clear_guest_offloads(vi);
> +			if (!prog)
> +				virtnet_restore_guest_offloads(vi);
> +		}
>  		if (old_prog)
>  			bpf_prog_put(old_prog);
>  		virtnet_napi_enable(vi->rq[i].vq, &vi->rq[i].napi);
> @@ -2588,6 +2644,10 @@ static int virtnet_probe(struct virtio_device *vdev)
>  		netif_carrier_on(dev);
>  	}
>  
> +	for (i = 0; i < ARRAY_SIZE(guest_offloads); i++)
> +		if (virtio_has_feature(vi->vdev, guest_offloads[i]))
> +			set_bit(guest_offloads[i], &vi->guest_offloads);
> +
>  	pr_debug("virtnet: registered device %s with %d RX and TX
vq's\n",
>  		 dev->name, max_queue_pairs);
>  
> @@ -2684,7 +2744,7 @@ static struct virtio_device_id id_table[] = {
>  	VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN, \
>  	VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, \
>  	VIRTIO_NET_F_CTRL_MAC_ADDR, \
> -	VIRTIO_NET_F_MTU
> +	VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS
>  
>  static unsigned int features[] = {
>  	VIRTNET_FEATURES,
> -- 
> 2.7.4

Michael S. Tsirkin

2017-Jul-24 21:41 UTC

head link

[PATCH net-next V2 0/5] Refine virtio-net XDP

On Mon, Jul 24, 2017 at 01:38:59PM -0700, David Miller
wrote:> From: Jason Wang <jasowang at redhat.com>
> Date: Wed, 19 Jul 2017 16:54:44 +0800
> 
> > Hi:
> > 
> > This series brings two optimizations for virtio-net XDP:
> > 
> > - avoid reset during XDP set
> > - turn off offloads on demand
> > 
> > Changes from V1:
> > - Various tweaks on commit logs and comments
> > - Use virtnet_napi_enable() when enabling NAPI on XDP set
> > - Copy the small buffer packet only if xdp_headroom is smaller than
> >   required
> > 
> > Please review.
> 
> Series applied, thanks Jason.
> 
> Michael, I gave you 4+ days to properly review this respin of this
> series.  I felt that was more than sufficient time, even with an
> intervening weekend.  So if you don't like that I applied this without
> your review, please be more punctual in the future.
> 
> Thank you.
My bad - reviewed when I was offline and forgot to send it out.

By luck this is not a big deal:

- Patches 1-4 are good.
- Patch 5 has some problems IMO, but all it does
is try to enable a previously non-working configuration, so
it seems ok to fix it up with follow-up patches as appropriate.

-- 
MST

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[PATCH net-next V2 5/5] virtio-net: switch off offloads on demand if possible on XDP set

[PATCH net-next V2 0/5] Refine virtio-net XDP

[PATCH net-next V2 5/5] virtio-net: switch off offloads on demand if possible on XDP set

[PATCH net-next V2 5/5] virtio-net: switch off offloads on demand if possible on XDP set

[PATCH net-next V2 0/5] Refine virtio-net XDP

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