[dpdk-dev] [PATCH v4]net/virtio: add mtu set in virtio

[Dey, Souvik]

I have already taken care of this in v5 of the patch , If possible please review the same .

-----Original Message-----
From: Yuanhan Liu [mailto:yuanhan.liu at linux.intel.com] 
Sent: Tuesday, September 20, 2016 3:12 AM
To: Kavanagh, Mark B <mark.b.kavanagh at intel.com>
Cc: Dey, Souvik <sodey at sonusnet.com>; dev at dpdk.org; stephen at networkplumber.org
Subject: Re: [PATCH v4]net/virtio: add mtu set in virtio

On Wed, Sep 14, 2016 at 12:15:37PM +0000, Kavanagh, Mark B wrote:
> >
> >>+{
> >>+       struct rte_eth_dev_info dev_info;
> >>+       uint32_t ether_hdr_len = ETHER_HDR_LEN + ETHER_CRC_LEN + 
> >>+VLAN_TAG_LEN;
> >>+       uint32_t frame_size = mtu + ether_hdr_len;
> >>+
> >>+       virtio_dev_info_get(dev, &dev_info);
> >>+
> >>+       if (mtu < dev_info.min_rx_bufsize || frame_size >
> >>+dev_info.max_rx_pktlen) {
> >
> >It's not clear to me whether 'mtu' in this case should be compared 
> >with ETHER_MIN_MTU, as per other DPDK drivers, or alternatively 
> >whether 'frame_size' should be compared with dev_info.min_rx_bufsize.
> >Any thoughts?
> >[Dey, Souvik] I am not sure why virtio min_rx_bufsize is less than 
> >ETHER_MIN_MTU, i think it will be good to have the  compare statement 
> >as If(frame_size < ETHER_MIN_MTU || frame_size > 
> >dev_info.max_rx_pktlen) , then error. What do you suggest ?
> 
> Again, this all depends on what 'mtu' means in this context.
> 
> Since you mentioned previously that it relates to the packet (i.e. L3) length, and not the frame (i.e. L2) length, I would suggest that the comparison should be:
> 
> 	if (mtu < ETHER_MIN_MTU || frame_size > dev_info.max_rx_pktlen)
> 
> Yuanhan, any thoughts on this?

I think you are right. At least, that's how the ixgbe PMD driver code looks like.

	--yliu