Re: [dpdk-dev] [PATCH v3] net/ixgbe: fix configuration of max frame size

["Guo, Jia" <jia.guo@intel.com>]

Hi, Alvin

> -----Original Message-----
> From: Zhang,Alvin <alvinx.zhang@intel.com>
> Sent: Friday, January 15, 2021 3:00 PM
> To: Guo, Jia <jia.guo@intel.com>; Wang, Haiyue <haiyue.wang@intel.com>;
> Xie, WeiX <weix.xie@intel.com>
> Cc: dev@dpdk.org; Zhang, AlvinX <alvinx.zhang@intel.com>;
> stable@dpdk.org
> Subject: [PATCH v3] net/ixgbe: fix configuration of max frame size
> 
> From: Alvin Zhang <alvinx.zhang@intel.com>
> 
> For 82599 NIC, jumbo frame feature is not supported in IOV mode, but if a VF
> requests to configure the frame size to that not bigger than
> RTE_ETHER_MAX_LEN, the PMD should not return -1.
> This patch keeps ixgbe PMD's handling mode consistent with kernel driver in
> above situation.
> 

Why it should not return -1 and what is the kernel driver behaviors related with this patch?

> In addition, the value set by the command IXGBE_VF_SET_LPE represents
> the max frame size, not the mtu.
> 
> Fixes: 1b9ea09c067b ("ixgbe: support X550")
> Fixes: 95a27b3ba5f5 ("net/ixgbe: enable jumbo frame for VF")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Alvin Zhang <alvinx.zhang@intel.com>
> ---
> 
> V3: Restore variable name from cur_frame_size to max_frs.
> ---
>  drivers/net/ixgbe/ixgbe_pf.c | 17 ++++++++++-------
>  1 file changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/ixgbe/ixgbe_pf.c b/drivers/net/ixgbe/ixgbe_pf.c
> index 833863a..1ffde56 100644
> --- a/drivers/net/ixgbe/ixgbe_pf.c
> +++ b/drivers/net/ixgbe/ixgbe_pf.c
> @@ -555,17 +555,20 @@ int ixgbe_pf_host_configure(struct rte_eth_dev
> *eth_dev)  ixgbe_set_vf_lpe(struct rte_eth_dev *dev, __rte_unused
> uint32_t vf, uint32_t *msgbuf)  {
>  	struct ixgbe_hw *hw = IXGBE_DEV_PRIVATE_TO_HW(dev->data-
> >dev_private);
> -	uint32_t new_mtu = msgbuf[1];
> +	uint32_t max_frame = msgbuf[1];
>  	uint32_t max_frs;
>  	uint32_t hlreg0;
> -	int max_frame = new_mtu + RTE_ETHER_HDR_LEN +
> RTE_ETHER_CRC_LEN;
> 
>  	/* X540 and X550 support jumbo frames in IOV mode */
>  	if (hw->mac.type != ixgbe_mac_X540 &&
>  		hw->mac.type != ixgbe_mac_X550 &&
>  		hw->mac.type != ixgbe_mac_X550EM_x &&
> -		hw->mac.type != ixgbe_mac_X550EM_a)
> -		return -1;
> +		hw->mac.type != ixgbe_mac_X550EM_a) {
> +		if (max_frame > dev->data-
> >dev_conf.rxmode.max_rx_pkt_len)

This condition is only for X540/X550?

> +			return -1;
> +
> +		return 0;
> +	}
> 

Assume that return 0 means success to set vf lpe, return -1 means failed to set vf lpe. If it is not support in VF, why return 0?

>  	if (max_frame < RTE_ETHER_MIN_LEN ||
>  			max_frame >
> RTE_ETHER_MAX_JUMBO_FRAME_LEN) @@ -573,9 +576,9 @@ int
> ixgbe_pf_host_configure(struct rte_eth_dev *eth_dev)
> 
>  	max_frs = (IXGBE_READ_REG(hw, IXGBE_MAXFRS) &
>  		   IXGBE_MHADD_MFS_MASK) >>
> IXGBE_MHADD_MFS_SHIFT;
> -	if (max_frs < new_mtu) {
> +	if (max_frs < max_frame) {
>  		hlreg0 = IXGBE_READ_REG(hw, IXGBE_HLREG0);
> -		if (new_mtu > RTE_ETHER_MAX_LEN) {
> +		if (max_frame > RTE_ETHER_MAX_LEN) {
>  			dev->data->dev_conf.rxmode.offloads |=
>  				DEV_RX_OFFLOAD_JUMBO_FRAME;
>  			hlreg0 |= IXGBE_HLREG0_JUMBOEN;
> @@ -586,7 +589,7 @@ int ixgbe_pf_host_configure(struct rte_eth_dev
> *eth_dev)
>  		}
>  		IXGBE_WRITE_REG(hw, IXGBE_HLREG0, hlreg0);
> 
> -		max_frs = new_mtu << IXGBE_MHADD_MFS_SHIFT;
> +		max_frs = max_frame << IXGBE_MHADD_MFS_SHIFT;
>  		IXGBE_WRITE_REG(hw, IXGBE_MAXFRS, max_frs);
>  	}
> 
> --
> 1.8.3.1