[dpdk-dev] [PATCH v2] net/e1000: update UPDATE_VF_STAT to handle rollover

Ferruh Yigit ferruh.yigit at intel.com
Wed Jan 29 11:10:05 CET 2020


On 1/26/2020 5:25 PM, David Harton wrote:
> Modified UPDATE_VF_STAT to properly handle rollover conditions.
> 
> Fixes: d82170d27918 ("igb: add VF support")
> Cc: intel.com
> 
> Signed-off-by: David Harton <dharton at cisco.com>
> ---
>  drivers/net/e1000/igb_ethdev.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/e1000/igb_ethdev.c b/drivers/net/e1000/igb_ethdev.c
> index a3e30dbe5..825663267 100644
> --- a/drivers/net/e1000/igb_ethdev.c
> +++ b/drivers/net/e1000/igb_ethdev.c
> @@ -261,11 +261,15 @@ static int igb_filter_restore(struct rte_eth_dev *dev);
>  /*
>   * Define VF Stats MACRO for Non "cleared on read" register
>   */
> -#define UPDATE_VF_STAT(reg, last, cur)            \
> -{                                                 \
> -	u32 latest = E1000_READ_REG(hw, reg);     \
> -	cur += (latest - last) & UINT_MAX;        \

Why this is wrong? Both 'latest' and 'last' are 'u32', so diff should be correct
'u32' value. And it is added to 'u64' 'cur' value. What I am missing?

> -	last = latest;                            \
> +#define UPDATE_VF_STAT(reg, last, cur)                          \
> +{                                                               \
> +	u32 latest = E1000_READ_REG(hw, reg);                   \
> +	if (latest >= last)                                     \
> +		cur += (latest - last);                         \
> +	else                                                    \
> +		cur += ((latest + ((uint64_t)1 << 32)) - last); \
> +	cur &= UINT_MAX;                                        \

Why & with UINT_MAX, won't this limit the value to 32bits which has 64bit storage?

> +	last = latest;                                          \
>  }
>  
>  #define IGB_FC_PAUSE_TIME 0x0680
> 



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