[dpdk-dev] [PATCH v5]net/virtio: add mtu set in virtio

[Kavanagh, Mark B]

>	
>

Hi Souvik,

There are some very basic errors in this patch, particularly with respect to format.
Review comments are inline - please address same and resubmit the patch. I also recommend running $DPDK_DIR/utilities/checkpatch.py on any future submissions.

Thanks,
Mark

>

As a general comment, please capitalize 'MTU' throughout the commit message.

>Virtio interfaces should also support setting of mtu, as in case of cloud

'also' is redundant in the above sentence - please remove it.
 
>it is expected to have the consistent mtu across the infrastructure that
>the dhcp server sends and not hardcoded to 1500(default).

Try to make the problem statement here more general, before going into specifics.
i.e. something along the lines of 
	"Virtio interfaces do not currently allow the user to specify a particular Maximum Transmission Unit (MTU).
       Consequently, the MTU of Virtio interfaces is typically set to the Ethernet default value of 1500.
       This is problematic in the case of cloud deployments, in which a specific (and potentially non-standard) MTU needs to be set by a DHCP server, and honored by all interfaces across the traffic path. ...., etc., etc."     

>In case when GRE/VXLAN tunneling is used, it adds overheads to the total

Please be specific in your description - what is 'it' in the above context?

>size of 1518, and in that cases the DHCP server corrects the L3 MTU to 1454
>to take care of the overhead. BUt since virtio interfaces was not having the

Should be lowercase 'u' in 'But' 

>mtu set that mtu sent by dhcp was ignored and teh instance will still send

Typo - 'teh'

>packets with 1500 mtu which afetr encapsulation will become more than 1518

Typo - 'afetr'

>and eventually gets dropped in the infrastructure. This issue can be solved
>by honoring the mtu 1454 sent by dhcp server, which this below patch will
>take care.

Explain how the patch resolves the issue (i.e. by adding an additional 'set_mtu' function to the Virtio driver, which can be leveraged by the dhcp server/controller).

>
>
>Changes in v5: Incorporated review comments.

It is implicit that a new patch version incorporates review comments.
To make things easier for the reviewer, please provide concise descriptions of the changes made/review comments addressed.

For example:
v5:
- Fix log message for out-of-bounds MTU parameter in virtio_mtu_set
- Calculate frame size, based on 'mtu' parameter, for upper bounds check in virtio_mtu_set
- ....
- etc., etc. 


>Changes in v4: Incorporated review comments.
>Changes in v3: Corrected few style errors as reported by sys-stv.
>Changes in v2: Incorporated review comments.
>
>Signed-off-by: Souvik Dey <sodey at sonusnet.com>
>
>---

Version history should not be part of the commit message - please move it to below this dashed line.

> drivers/net/virtio/virtio_ethdev.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
>diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
>index 07d6449..da16ad4 100644
>--- a/drivers/net/virtio/virtio_ethdev.c
>+++ b/drivers/net/virtio/virtio_ethdev.c
>@@ -653,12 +653,20 @@ virtio_dev_allmulticast_disable(struct rte_eth_dev *dev)
>                PMD_INIT_LOG(ERR, "Failed to disable allmulticast");
> }
>
>+#define VLAN_TAG_SIZE           4    /* 802.3ac tag (not DMA'd) */
>+
>+static int  virtio_mtu_set(struct rte_eth_dev *dev, uint16_t mtu)

Additional whitespace between 'int' and 'virtio_mtu_set' - please remove.

>+{
>+       struct rte_eth_dev_info dev_info;
>+       uint32_t ether_hdr_len = ETHER_HDR_LEN + ETHER_CRC_LEN + VLAN_TAG_SIZE;
>+       uint32_t frame_size = mtu + ether_hdr_len;
>+
>+       virtio_dev_info_get(dev, &dev_info);
>+
>+       if (frame_size < ETHER_MIN_MTU || frame_size > dev_info.max_rx_pktlen) {
>+               PMD_INIT_LOG(ERR, "MTU should be between %d and %d\n",
>+                               (ETHER_MIN_MTU - ether_hdr_len),
>+                               (dev_info.max_rx_pktlen - ether_hdr_len));
>+               return -EINVAL;
>+       }
>+       return 0;
>+}
>@@ -677,7 +685,6 @@ static const struct eth_dev_ops virtio_eth_dev_ops = {
>        .allmulticast_enable     = virtio_dev_allmulticast_enable,
>        .allmulticast_disable    = virtio_dev_allmulticast_disable,
>+       .mtu_set                 = virtio_mtu_set,
>        .dev_infos_get           = virtio_dev_info_get,
>        .stats_get               = virtio_dev_stats_get,
>        .xstats_get              = virtio_dev_xstats_get,
>--
>2.9.3.windows.1