[dpdk-stable] [PATCH] net/tap: fix missing _SC_IOV_MAX

[Wiles, Keith]

> On Mar 7, 2019, at 4:25 PM, olegpoly123 <olegp123 at walla.co.il> wrote:
> 
> If the value _SC_IOV_MAX is missing, sysconf returns -1.
> In this case, iov_max is set to a default value of 1024.
> 
> Cc: stable at dpdk.org
> 
> Signed-off-by: Oeg Polyakov <opolyakov at northforgeinc.com>
> ---
> drivers/net/tap/rte_eth_tap.c | 5 +++++
> 1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
> index 6f5109fca..cd48b2b2a 100644
> --- a/drivers/net/tap/rte_eth_tap.c
> +++ b/drivers/net/tap/rte_eth_tap.c
> @@ -1326,6 +1326,11 @@ tap_rx_queue_setup(struct rte_eth_dev *dev,
> 	struct rx_queue *rxq = &internals->rxq[rx_queue_id];
> 	struct rte_mbuf **tmp = &rxq->pool;
> 	long iov_max = sysconf(_SC_IOV_MAX);
> +	if (iov_max <= 0) {
> +		TAP_LOG(WARNING,
> +			"_SC_IOV_MAX is not defined. Using 1024 as default\n");
> +		iov_max = 1024;

Can I get you to create a define for the 1024 value e.g. #define TAP_IOV_DEFAULT_MAX 1024 or something of that type.
Also change the TAP_LOG to use the define. 
> +	}
> 	uint16_t nb_desc = RTE_MIN(nb_rx_desc, iov_max - 1);
> 	struct iovec (*iovecs)[nb_desc + 1];
> 	int data_off = RTE_PKTMBUF_HEADROOM;
> -- 
> 2.14.1
> 

Regards,
Keith