RE: [PATCH v3 net-next] net: hyperv: Add attributes to show TX indirection table

[Haiyang Zhang <haiyangz@microsoft.com>]

> -----Original Message-----
> From: Chi Song <Song.Chi@microsoft.com>
> Sent: Monday, July 20, 2020 3:17 AM
> To: KY Srinivasan <kys@microsoft.com>; Haiyang Zhang
> <haiyangz@microsoft.com>; Stephen Hemminger <sthemmin@microsoft.com>;
> Wei Liu <wei.liu@kernel.org>; David S. Miller <davem@davemloft.net>; Jakub
> Kicinski <kuba@kernel.org>
> Cc: linux-hyperv@vger.kernel.org; netdev@vger.kernel.org; linux-
> kernel@vger.kernel.org
> Subject: [PATCH v3 net-next] net: hyperv: Add attributes to show TX indirection
> table
> 
> An imbalanced TX indirection table causes netvsc to have low
> performance. This table is created and managed during runtime. To help
> better diagnose performance issues caused by imbalanced tables, add
> device attributes to show the content of TX indirection tables.
> 
> Signed-off-by: Chi Song <chisong@microsoft.com>
> ---
> v2: remove RX as it's in ethtool already, show single value in each file,
>  and update description.
> v3: fix broken format by alpine.
> 
> Thank you for comments. Let me know, if I miss something.
> 
> ---
>  drivers/net/hyperv/netvsc_drv.c | 53 +++++++++++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
> 
> diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
> index 6267f706e8ee..222c2fad9300 100644
> --- a/drivers/net/hyperv/netvsc_drv.c
> +++ b/drivers/net/hyperv/netvsc_drv.c
> @@ -2370,6 +2370,55 @@ static int netvsc_unregister_vf(struct net_device
> *vf_netdev)
>  	return NOTIFY_OK;
>  }
> 
> +static struct device_attribute
> dev_attr_netvsc_dev_attrs[VRSS_SEND_TAB_SIZE];
> +static struct attribute *netvsc_dev_attrs[VRSS_SEND_TAB_SIZE + 1];
> +
> +const struct attribute_group netvsc_dev_group = {
> +	.name = NULL,
> +	.attrs = netvsc_dev_attrs,
> +};
> +
> +static ssize_t tx_indirection_table_show(struct device *dev,
> +					 struct device_attribute *dev_attr,
> +					 char *buf)
> +{
> +	struct net_device *ndev = to_net_dev(dev);
> +	struct net_device_context *ndc = netdev_priv(ndev);
> +	ssize_t offset = 0;
> +	int index = dev_attr - dev_attr_netvsc_dev_attrs;
> +
> +	offset = sprintf(buf, "%u\n", ndc->tx_table[index]);
> +
> +	return offset;
> +}
> +
> +static void netvsc_attrs_init(void)
> +{
> +	int i;
> +	char buffer[32];
> +
> +	for (i = 0; i < VRSS_SEND_TAB_SIZE; i++) {
> +		sprintf(buffer, "tx_indirection_table_%02u", i);
> +		dev_attr_netvsc_dev_attrs[i].attr.name =
> +			kstrdup(buffer, GFP_KERNEL);
> +		dev_attr_netvsc_dev_attrs[i].attr.mode = 0444;
> +		sysfs_attr_init(&dev_attr_netvsc_dev_attrs[i].attr);
> +
> +		dev_attr_netvsc_dev_attrs[i].show = tx_indirection_table_show;
> +		dev_attr_netvsc_dev_attrs[i].store = NULL;
> +		netvsc_dev_attrs[i] = &dev_attr_netvsc_dev_attrs[i].attr;
> +	}
> +	netvsc_dev_attrs[VRSS_SEND_TAB_SIZE] = NULL;
> +}
> +
> +static void netvsc_attrs_exit(void)
> +{
> +	int i;
> +
> +	for (i = 0; i < VRSS_SEND_TAB_SIZE; i++)
> +		kfree(dev_attr_netvsc_dev_attrs[i].attr.name);
> +}
> +
>  static int netvsc_probe(struct hv_device *dev,
>  			const struct hv_vmbus_device_id *dev_id)
>  {
> @@ -2396,6 +2445,7 @@ static int netvsc_probe(struct hv_device *dev,
>  			   net_device_ctx->msg_enable);
> 
>  	hv_set_drvdata(dev, net);
> +	netvsc_attrs_init();

dev_attr_netvsc_dev_attrs is a global array, so it should be initialized 
and cleaned up in netvsc_drv_init/exit(). 
If there are multiple NICs and possible hot add/remove, init/cleaning it in 
netvsc_probe/remove() will cause memory leak, and/or use of freed 
memory.

Thanks,
- Haiyang