Subject: Re: [PATCH net-next v3 3/6] virtio_net: support device stats

From: Simon Horman <[email-masked]>
Date: Tue, 27 Feb 2024 19:19:40 +0000

On Tue, Feb 27, 2024 at 04:03:00PM +0800, Xuan Zhuo wrote:
> As the spec https://github.com/oasis-tcs/virtio-spec/commit/42f389989823039724f95bbbd243291ab0064f82
> 
> make virtio-net support getting the stats from the device by ethtool -S
> <eth0>.
> 
> Signed-off-by: Xuan Zhuo <[email-masked]>

...

> +static int virtnet_get_hw_stats(struct virtnet_info *vi,
> +				struct virtnet_stats_ctx *ctx)
> +{
> +	struct virtio_net_ctrl_queue_stats *req;
> +	struct virtio_net_stats_reply_hdr *hdr;
> +	struct scatterlist sgs_in, sgs_out;
> +	u32 num_rx, num_tx, num_cq, offset;
> +	int qnum, i, j,  qid, res_size;
> +	struct virtnet_stats_map *m;
> +	void *reply, *p;
> +	u64 bitmap;
> +	int ok;
> +	u64 *v;
> +
> +	if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_DEVICE_STATS))
> +		return 0;
> +
> +	qnum = 0;
> +	if (ctx->bitmap_cq)
> +		qnum += 1;
> +
> +	if (ctx->bitmap_rx)
> +		qnum += vi->curr_queue_pairs;
> +
> +	if (ctx->bitmap_tx)
> +		qnum += vi->curr_queue_pairs;
> +
> +	req = kcalloc(qnum, sizeof(*req), GFP_KERNEL);
> +	if (!req)
> +		return -ENOMEM;
> +
> +	res_size = (ctx->size_rx + ctx->size_tx) * vi->curr_queue_pairs + ctx->size_cq;
> +	reply = kmalloc(res_size, GFP_KERNEL);
> +	if (!reply) {
> +		kfree(req);
> +		return -ENOMEM;
> +	}
> +
> +	j = 0;
> +	for (i = 0; i < vi->curr_queue_pairs; ++i) {
> +		if (ctx->bitmap_rx) {
> +			req->stats[j].vq_index = cpu_to_le16(i * 2);
> +			req->stats[j].types_bitmap[0] = cpu_to_le64(ctx->bitmap_rx);
> +			++j;
> +		}
> +
> +		if (ctx->bitmap_tx) {
> +			req->stats[j].vq_index = cpu_to_le16(i * 2 + 1);
> +			req->stats[j].types_bitmap[0] = cpu_to_le64(ctx->bitmap_tx);
> +			++j;
> +		}
> +	}
> +
> +	if (ctx->size_cq) {
> +		req->stats[j].vq_index = cpu_to_le16(vi->max_queue_pairs * 2);
> +		req->stats[j].types_bitmap[0] = cpu_to_le64(ctx->bitmap_cq);
> +		++j;
> +	}
> +
> +	sg_init_one(&sgs_out, req, sizeof(*req) * j);
> +	sg_init_one(&sgs_in, reply, res_size);
> +
> +	ok = virtnet_send_command(vi, VIRTIO_NET_CTRL_STATS,
> +				  VIRTIO_NET_CTRL_STATS_GET,
> +				  &sgs_out, &sgs_in);
> +	kfree(req);
> +
> +	if (!ok) {
> +		kfree(reply);
> +		return ok;
> +	}
> +
> +	num_rx = VIRTNET_RQ_STATS_LEN + ctx->num_rx;
> +	num_tx = VIRTNET_SQ_STATS_LEN + ctx->num_tx;
> +	num_cq = ctx->num_tx;
> +
> +	for (p = reply; p - reply < res_size; p += le16_to_cpu(hdr->size)) {
> +		hdr = p;
> +
> +		qid = le16_to_cpu(hdr->vq_index);
> +
> +		if (qid == vi->max_queue_pairs * 2) {
> +			offset = 0;
> +			bitmap = ctx->bitmap_cq;
> +		} else if (qid % 2) {
> +			offset = num_cq + num_rx * vi->curr_queue_pairs + num_tx * (qid / 2);
> +			offset += VIRTNET_SQ_STATS_LEN;
> +			bitmap = ctx->bitmap_tx;
> +		} else {
> +			offset = num_cq + num_rx * (qid / 2) + VIRTNET_RQ_STATS_LEN;
> +			bitmap = ctx->bitmap_rx;
> +		}
> +
> +		for (i = 0; i < ARRAY_SIZE(virtio_net_stats_map); ++i) {
> +			m = &virtio_net_stats_map[i];
> +
> +			if (m->stat_type & bitmap)
> +				offset += m->num;
> +
> +			if (hdr->type != m->reply_type)
> +				continue;
> +
> +			for (j = 0; j < m->num; ++j) {
> +				v = p + m->desc[j].offset;
> +				ctx->data[offset + j] = le64_to_cpu(*v);

Hi Xuan Zhuo,

Sparse complains about the line above because the type of *v is u64,
but le64_to_cpu() expects __le64.

> +			}
> +
> +			break;
> +		}
> +	}
> +
> +	kfree(reply);
> +	return 0;
> +}
> +
>  static void virtnet_get_strings(struct net_device *dev, u32 stringset, u8 *data)
>  {
>  	struct virtnet_info *vi = netdev_priv(dev);

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