Re: [PATCH net-next 3/4] virtio_net: Use new RSS config structs

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On 2025/03/19 10:22, Xuan Zhuo wrote:

On Tue, 18 Mar 2025 18:56:53 +0900, Akihiko Odaki <akihiko.odaki@xxxxxxxxxx> wrote:

The new RSS configuration structures allow easily constructing data for
VIRTIO_NET_CTRL_MQ_RSS_CONFIG as they strictly follow the order of data
for the command.

Signed-off-by: Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>
---
  drivers/net/virtio_net.c | 117 +++++++++++++++++------------------------------
  1 file changed, 43 insertions(+), 74 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index d1ed544ba03a..4153a0a5f278 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -360,24 +360,7 @@ struct receive_queue {
  	struct xdp_buff **xsk_buffs;
  };

-/* This structure can contain rss message with maximum settings for indirection table and keysize
- * Note, that default structure that describes RSS configuration virtio_net_rss_config
- * contains same info but can't handle table values.
- * In any case, structure would be passed to virtio hw through sg_buf split by parts
- * because table sizes may be differ according to the device configuration.
- */
  #define VIRTIO_NET_RSS_MAX_KEY_SIZE     40
-struct virtio_net_ctrl_rss {
-	__le32 hash_types;
-	__le16 indirection_table_mask;
-	__le16 unclassified_queue;
-	__le16 hash_cfg_reserved; /* for HASH_CONFIG (see virtio_net_hash_config for details) */
-	__le16 max_tx_vq;
-	u8 hash_key_length;
-	u8 key[VIRTIO_NET_RSS_MAX_KEY_SIZE];
-
-	__le16 *indirection_table;
-};

  /* Control VQ buffers: protected by the rtnl lock */
  struct control_buf {
@@ -421,7 +404,9 @@ struct virtnet_info {
  	u16 rss_indir_table_size;
  	u32 rss_hash_types_supported;
  	u32 rss_hash_types_saved;
-	struct virtio_net_ctrl_rss rss;
+	struct virtio_net_rss_config_hdr *rss_hdr;
+	struct virtio_net_rss_config_trailer rss_trailer;
+	u8 rss_hash_key_data[VIRTIO_NET_RSS_MAX_KEY_SIZE];


Why put rss_hash_key_data outside of virtio_net_rss_config_trailer?
virtio_net_rss_config_trailer has a field named hash_key_data, but it is a flexible array without storage. The structure is defined in a UAPI header, and its other users may provide storages of different sizes. So we need to provide a storage with our own size limit. 

Regards,
Akihiko Odaki



Thanks.




  	/* Has control virtqueue */
  	bool has_cvq;
@@ -523,23 +508,16 @@ enum virtnet_xmit_type {
  	VIRTNET_XMIT_TYPE_XSK,
  };

-static int rss_indirection_table_alloc(struct virtio_net_ctrl_rss *rss, u16 indir_table_size)
+static size_t virtnet_rss_hdr_size(const struct virtnet_info *vi)
  {
-	if (!indir_table_size) {
-		rss->indirection_table = NULL;
-		return 0;
-	}
+	u16 indir_table_size = vi->has_rss ? vi->rss_indir_table_size : 1;

-	rss->indirection_table = kmalloc_array(indir_table_size, sizeof(u16), GFP_KERNEL);
-	if (!rss->indirection_table)
-		return -ENOMEM;
-
-	return 0;
+	return struct_size(vi->rss_hdr, indirection_table, indir_table_size);
  }

-static void rss_indirection_table_free(struct virtio_net_ctrl_rss *rss)
+static size_t virtnet_rss_trailer_size(const struct virtnet_info *vi)
  {
-	kfree(rss->indirection_table);
+	return struct_size(&vi->rss_trailer, hash_key_data, vi->rss_key_size);
  }

  /* We use the last two bits of the pointer to distinguish the xmit type. */
@@ -3576,15 +3554,16 @@ static void virtnet_rss_update_by_qpairs(struct virtnet_info *vi, u16 queue_pair

  	for (; i < vi->rss_indir_table_size; ++i) {
  		indir_val = ethtool_rxfh_indir_default(i, queue_pairs);
-		vi->rss.indirection_table[i] = cpu_to_le16(indir_val);
+		vi->rss_hdr->indirection_table[i] = cpu_to_le16(indir_val);
  	}
-	vi->rss.max_tx_vq = cpu_to_le16(queue_pairs);
+	vi->rss_trailer.max_tx_vq = cpu_to_le16(queue_pairs);
  }

  static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
  {
  	struct virtio_net_ctrl_mq *mq __free(kfree) = NULL;
-	struct virtio_net_ctrl_rss old_rss;
+	struct virtio_net_rss_config_hdr *old_rss_hdr;
+	struct virtio_net_rss_config_trailer old_rss_trailer;
  	struct net_device *dev = vi->dev;
  	struct scatterlist sg;

@@ -3599,24 +3578,28 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
  	 * update (VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET below) and return directly.
  	 */
  	if (vi->has_rss && !netif_is_rxfh_configured(dev)) {
-		memcpy(&old_rss, &vi->rss, sizeof(old_rss));
-		if (rss_indirection_table_alloc(&vi->rss, vi->rss_indir_table_size)) {
-			vi->rss.indirection_table = old_rss.indirection_table;
+		old_rss_hdr = vi->rss_hdr;
+		old_rss_trailer = vi->rss_trailer;
+		vi->rss_hdr = kmalloc(virtnet_rss_hdr_size(vi), GFP_KERNEL);
+		if (!vi->rss_hdr) {
+			vi->rss_hdr = old_rss_hdr;
  			return -ENOMEM;
  		}

+		*vi->rss_hdr = *old_rss_hdr;
  		virtnet_rss_update_by_qpairs(vi, queue_pairs);

  		if (!virtnet_commit_rss_command(vi)) {
  			/* restore ctrl_rss if commit_rss_command failed */
-			rss_indirection_table_free(&vi->rss);
-			memcpy(&vi->rss, &old_rss, sizeof(old_rss));
+			kfree(vi->rss_hdr);
+			vi->rss_hdr = old_rss_hdr;
+			vi->rss_trailer = old_rss_trailer;

  			dev_warn(&dev->dev, "Fail to set num of queue pairs to %d, because committing RSS failed\n",
  				 queue_pairs);
  			return -EINVAL;
  		}
-		rss_indirection_table_free(&old_rss);
+		kfree(old_rss_hdr);
  		goto succ;
  	}

@@ -4059,28 +4042,12 @@ static int virtnet_set_ringparam(struct net_device *dev,
  static bool virtnet_commit_rss_command(struct virtnet_info *vi)
  {
  	struct net_device *dev = vi->dev;
-	struct scatterlist sgs[4];
-	unsigned int sg_buf_size;
+	struct scatterlist sgs[2];

  	/* prepare sgs */
-	sg_init_table(sgs, 4);
-
-	sg_buf_size = offsetof(struct virtio_net_ctrl_rss, hash_cfg_reserved);
-	sg_set_buf(&sgs[0], &vi->rss, sg_buf_size);
-
-	if (vi->has_rss) {
-		sg_buf_size = sizeof(uint16_t) * vi->rss_indir_table_size;
-		sg_set_buf(&sgs[1], vi->rss.indirection_table, sg_buf_size);
-	} else {
-		sg_set_buf(&sgs[1], &vi->rss.hash_cfg_reserved, sizeof(uint16_t));
-	}
-
-	sg_buf_size = offsetof(struct virtio_net_ctrl_rss, key)
-			- offsetof(struct virtio_net_ctrl_rss, max_tx_vq);
-	sg_set_buf(&sgs[2], &vi->rss.max_tx_vq, sg_buf_size);
-
-	sg_buf_size = vi->rss_key_size;
-	sg_set_buf(&sgs[3], vi->rss.key, sg_buf_size);
+	sg_init_table(sgs, 2);
+	sg_set_buf(&sgs[0], vi->rss_hdr, virtnet_rss_hdr_size(vi));
+	sg_set_buf(&sgs[1], &vi->rss_trailer, virtnet_rss_trailer_size(vi));

  	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MQ,
  				  vi->has_rss ? VIRTIO_NET_CTRL_MQ_RSS_CONFIG
@@ -4097,17 +4064,17 @@ static bool virtnet_commit_rss_command(struct virtnet_info *vi)

  static void virtnet_init_default_rss(struct virtnet_info *vi)
  {
-	vi->rss.hash_types = cpu_to_le32(vi->rss_hash_types_supported);
+	vi->rss_hdr->hash_types = cpu_to_le32(vi->rss_hash_types_supported);
  	vi->rss_hash_types_saved = vi->rss_hash_types_supported;
-	vi->rss.indirection_table_mask = vi->rss_indir_table_size
+	vi->rss_hdr->indirection_table_mask = vi->rss_indir_table_size
  						? cpu_to_le16(vi->rss_indir_table_size - 1) : 0;
-	vi->rss.unclassified_queue = 0;
+	vi->rss_hdr->unclassified_queue = 0;

  	virtnet_rss_update_by_qpairs(vi, vi->curr_queue_pairs);

-	vi->rss.hash_key_length = vi->rss_key_size;
+	vi->rss_trailer.hash_key_length = vi->rss_key_size;

-	netdev_rss_key_fill(vi->rss.key, vi->rss_key_size);
+	netdev_rss_key_fill(vi->rss_hash_key_data, vi->rss_key_size);
  }

  static void virtnet_get_hashflow(const struct virtnet_info *vi, struct ethtool_rxnfc *info)
@@ -4218,7 +4185,7 @@ static bool virtnet_set_hashflow(struct virtnet_info *vi, struct ethtool_rxnfc *

  	if (new_hashtypes != vi->rss_hash_types_saved) {
  		vi->rss_hash_types_saved = new_hashtypes;
-		vi->rss.hash_types = cpu_to_le32(vi->rss_hash_types_saved);
+		vi->rss_hdr->hash_types = cpu_to_le32(vi->rss_hash_types_saved);
  		if (vi->dev->features & NETIF_F_RXHASH)
  			return virtnet_commit_rss_command(vi);
  	}
@@ -5398,11 +5365,11 @@ static int virtnet_get_rxfh(struct net_device *dev,

  	if (rxfh->indir) {
  		for (i = 0; i < vi->rss_indir_table_size; ++i)
-			rxfh->indir[i] = le16_to_cpu(vi->rss.indirection_table[i]);
+			rxfh->indir[i] = le16_to_cpu(vi->rss_hdr->indirection_table[i]);
  	}

  	if (rxfh->key)
-		memcpy(rxfh->key, vi->rss.key, vi->rss_key_size);
+		memcpy(rxfh->key, vi->rss_hash_key_data, vi->rss_key_size);

  	rxfh->hfunc = ETH_RSS_HASH_TOP;

@@ -5426,7 +5393,7 @@ static int virtnet_set_rxfh(struct net_device *dev,
  			return -EOPNOTSUPP;

  		for (i = 0; i < vi->rss_indir_table_size; ++i)
-			vi->rss.indirection_table[i] = cpu_to_le16(rxfh->indir[i]);
+			vi->rss_hdr->indirection_table[i] = cpu_to_le16(rxfh->indir[i]);
  		update = true;
  	}

@@ -5438,7 +5405,7 @@ static int virtnet_set_rxfh(struct net_device *dev,
  		if (!vi->has_rss && !vi->has_rss_hash_report)
  			return -EOPNOTSUPP;

-		memcpy(vi->rss.key, rxfh->key, vi->rss_key_size);
+		memcpy(vi->rss_hash_key_data, rxfh->key, vi->rss_key_size);
  		update = true;
  	}

@@ -6044,9 +6011,9 @@ static int virtnet_set_features(struct net_device *dev,

  	if ((dev->features ^ features) & NETIF_F_RXHASH) {
  		if (features & NETIF_F_RXHASH)
-			vi->rss.hash_types = cpu_to_le32(vi->rss_hash_types_saved);
+			vi->rss_hdr->hash_types = cpu_to_le32(vi->rss_hash_types_saved);
  		else
-			vi->rss.hash_types = cpu_to_le32(VIRTIO_NET_HASH_REPORT_NONE);
+			vi->rss_hdr->hash_types = cpu_to_le32(VIRTIO_NET_HASH_REPORT_NONE);

  		if (!virtnet_commit_rss_command(vi))
  			return -EINVAL;
@@ -6735,9 +6702,11 @@ static int virtnet_probe(struct virtio_device *vdev)
  			virtio_cread16(vdev, offsetof(struct virtio_net_config,
  				rss_max_indirection_table_length));
  	}
-	err = rss_indirection_table_alloc(&vi->rss, vi->rss_indir_table_size);
-	if (err)
+	vi->rss_hdr = kmalloc(virtnet_rss_hdr_size(vi), GFP_KERNEL);
+	if (!vi->rss_hdr) {
+		err = -ENOMEM;
  		goto free;
+	}

  	if (vi->has_rss || vi->has_rss_hash_report) {
  		vi->rss_key_size =
@@ -7016,7 +6985,7 @@ static void virtnet_remove(struct virtio_device *vdev)

  	remove_vq_common(vi);

-	rss_indirection_table_free(&vi->rss);
+	kfree(vi->rss_hdr);

  	free_netdev(vi->dev);
  }

--
2.48.1
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