[dpdk-dev] [RFC 02/14] virtio: use eth_link_read/write (and bug fix)

[Andrew Rybchenko]

On 07/14/2017 09:30 PM, Stephen Hemminger wrote:
> Use the new code in ethdev to handle link status update.
> Also, virtio was not correctly setting the autoneg flags
> since its speed should be marked as fixed.
>
> Signed-off-by: Stephen Hemminger <sthemmin at microsoft.com>
> ---
>   drivers/net/virtio/virtio_ethdev.c | 54 +++++---------------------------------
>   1 file changed, 6 insertions(+), 48 deletions(-)
>
> diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
> index 00a3122780ba..776ad4961a37 100644
> --- a/drivers/net/virtio/virtio_ethdev.c
> +++ b/drivers/net/virtio/virtio_ethdev.c
> @@ -43,7 +43,6 @@
>   #include <rte_string_fns.h>
>   #include <rte_memzone.h>
>   #include <rte_malloc.h>
> -#include <rte_atomic.h>
>   #include <rte_branch_prediction.h>
>   #include <rte_pci.h>
>   #include <rte_ether.h>
> @@ -794,46 +793,6 @@ static const struct eth_dev_ops virtio_eth_dev_ops = {
>   	.mac_addr_set            = virtio_mac_addr_set,
>   };
>   
> -static inline int
> -virtio_dev_atomic_read_link_status(struct rte_eth_dev *dev,
> -				struct rte_eth_link *link)
> -{
> -	struct rte_eth_link *dst = link;
> -	struct rte_eth_link *src = &(dev->data->dev_link);
> -
> -	if (rte_atomic64_cmpset((uint64_t *)dst, *(uint64_t *)dst,
> -			*(uint64_t *)src) == 0)
> -		return -1;
> -
> -	return 0;
> -}
> -
> -/**
> - * Atomically writes the link status information into global
> - * structure rte_eth_dev.
> - *
> - * @param dev
> - *   - Pointer to the structure rte_eth_dev to read from.
> - *   - Pointer to the buffer to be saved with the link status.
> - *
> - * @return
> - *   - On success, zero.
> - *   - On failure, negative value.
> - */
> -static inline int
> -virtio_dev_atomic_write_link_status(struct rte_eth_dev *dev,
> -		struct rte_eth_link *link)
> -{
> -	struct rte_eth_link *dst = &(dev->data->dev_link);
> -	struct rte_eth_link *src = link;
> -
> -	if (rte_atomic64_cmpset((uint64_t *)dst, *(uint64_t *)dst,
> -					*(uint64_t *)src) == 0)
> -		return -1;
> -
> -	return 0;
> -}
> -
>   static void
>   virtio_update_stats(struct rte_eth_dev *dev, struct rte_eth_stats *stats)
>   {
> @@ -1829,20 +1788,20 @@ virtio_dev_stop(struct rte_eth_dev *dev)
>   
>   	hw->started = 0;
>   	memset(&link, 0, sizeof(link));
> -	virtio_dev_atomic_write_link_status(dev, &link);
> +	_rte_eth_link_update(dev, &link);
>   }
>   
>   static int
>   virtio_dev_link_update(struct rte_eth_dev *dev, __rte_unused int wait_to_complete)
>   {
> -	struct rte_eth_link link, old;
> -	uint16_t status;
>   	struct virtio_hw *hw = dev->data->dev_private;
> +	struct rte_eth_link link;
> +	uint16_t status;
> +
>   	memset(&link, 0, sizeof(link));
> -	virtio_dev_atomic_read_link_status(dev, &link);
> -	old = link;
>   	link.link_duplex = ETH_LINK_FULL_DUPLEX;
>   	link.link_speed  = SPEED_10G;
> +	link.link_autoneg = ETH_LINK_SPEED_FIXED;

As I understand link_autoneg is 1 bit field with boolean semantics. I.e. 0/false - no autoneg, 1/true - autoneg.
It looks like it has wrong comment:
         uint16_t link_autoneg : 1;  /**< ETH_LINK_SPEED_[AUTONEG/FIXED] */

since
#define ETH_LINK_SPEED_AUTONEG  (0 <<  0)  /**< Autonegotiate (all speeds) */
#define ETH_LINK_SPEED_FIXED    (1 <<  0)  /**< Disable autoneg (fixed speed) */

whereas
#define ETH_LINK_FIXED          0 /**< No autonegotiation. */
#define ETH_LINK_AUTONEG        1 /**< Autonegotiated. */

In general this attempt to introduce bug is the result of wrong comment which is caused by very similar
defines with opposite values.

>   	if (hw->started == 0) {
>   		link.link_status = ETH_LINK_DOWN;
> @@ -1863,9 +1822,8 @@ virtio_dev_link_update(struct rte_eth_dev *dev, __rte_unused int wait_to_complet
>   	} else {
>   		link.link_status = ETH_LINK_UP;
>   	}
> -	virtio_dev_atomic_write_link_status(dev, &link);
>   
> -	return (old.link_status == link.link_status) ? -1 : 0;
> +	return _rte_eth_link_update(dev, &link);
>   }
>   
>   static void