[dpdk-dev] [PATCH v6] net/virtio: add set_mtu in virtio

[Dey, Souvik]

Hi Liu/Mark/Stephen,

              I have tried to modify the code with all of your latest comments. Do let me know if this looks fine or you have more comments.



Changes done :

-- max frame ize is compare to VIRTIO_MAX_RX_PKTLEN instead of dev_info.max_rx_pktlen

-- removed the CRC_LEN from the ether_len calculation and added the merge rx buf hdr len. ether_hdr_len = ETHER_HDR_LEN + VLAN_TAG_SIZE + hw->vtnet_hdr_size

-- Still retained the VLAN Size as the worst case scenario.





--

drivers/net/virtio/virtio_ethdev.c | 16 ++++++++++++++++

1 file changed, 16 insertions(+)



diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c

index 423c597..1dbfea6 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)

+{

+            struct virtio_hw *hw = dev->data->dev_private;

+            uint32_t ether_hdr_len = ETHER_HDR_LEN + VLAN_TAG_SIZE + hw->vtnet_hdr_size;

+            uint32_t frame_size = mtu + ether_hdr_len;

+

+            if (mtu < ETHER_MIN_MTU || frame_size > VIRTIO_MAX_RX_PKTLEN ) {

+                           PMD_INIT_LOG(ERR, "MTU should be between %d and %d\n",

+                                         ETHER_MIN_MTU, VIRTIO_MAX_RX_PKTLEN);

+                           return -EINVAL;

+            }

+            return 0;

+}



/*

  * dev_ops for virtio, bare necessities for basic operation

  */

@@ -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,

--

Please do let me know if this looks good to you all. Thanks



--

Regards,

Souvik



-----Original Message-----
From: Kavanagh, Mark B [mailto:mark.b.kavanagh at intel.com]
Sent: Friday, September 23, 2016 5:08 AM
To: Yuanhan Liu <yuanhan.liu at linux.intel.com>; Stephen Hemminger <stephen at networkplumber.org>
Cc: Dey, Souvik <sodey at sonusnet.com>; dev at dpdk.org
Subject: RE: [PATCH v6] net/virtio: add set_mtu in virtio



>Subject: Re: [PATCH v6] net/virtio: add set_mtu in virtio

>

>On Wed, Sep 21, 2016 at 06:45:05PM -0700, Stephen Hemminger wrote:

>> On Thu, 22 Sep 2016 00:08:38 +0000

>> "Dey, Souvik" <sodey at sonusnet.com<mailto:sodey at sonusnet.com>> wrote:

>>

>> > Answers inline.

>> >

>> > --

>> > Regards,

>> > Souvik

>> >

>> > -----Original Message-----

>> > From: Stephen Hemminger [mailto:stephen at networkplumber.org]

>> > Sent: Wednesday, September 21, 2016 7:22 PM

>> > To: Dey, Souvik <sodey at sonusnet.com<mailto:sodey at sonusnet.com>>

>> > Cc: mark.b.kavanagh at intel.com<mailto:mark.b.kavanagh at intel.com>; yuanhan.liu at linux.intel.com<mailto:yuanhan.liu at linux.intel.com>;

>> > dev at dpdk.org<mailto:dev at dpdk.org>

>> > Subject: Re: [PATCH v6] net/virtio: add set_mtu in virtio

>> >

>> > On Wed, 21 Sep 2016 19:11:47 -0400

>> > Dey <sodey at sonusnet.com<mailto:sodey at sonusnet.com>> wrote:

>> >

>> > >

>> > > +

>> > > +#define VLAN_TAG_SIZE           4    /* 802.3ac tag (not DMA'd) */

>> > > +

>> > > +static int virtio_mtu_set(struct rte_eth_dev *dev, uint16_t mtu) {

>> > > +       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 (mtu < 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,

>> > > +                               (dev_info.max_rx_pktlen - ether_hdr_len));

>> > > +               return -EINVAL;

>> > > +       }

>> > > +       return 0;

>> > > +}

>> >

>> > I am fine with the general idea of this patch but:

>> >   1. Calling virtio_dev_info_get is needlessly wasteful when all you want

>> >      is to access the max packet length. Since max_rx_pktlen is always

>> >      VIRTIO_MAX_RX_PKTLEN, please just use that.

>> > [Dey, Souvik] I am using the virtio_dev_info_get as in future

>> > can/may support the

>max_rx_pktlen as a variable to be set by  the application. This will

>keep the changes future proof. As we need to support till 65535 instead of 9728 as the linux does.

>>

>> Fine, then just dereference hw->rx_max_pktlen. Driver code can/should

>> reference its own data directly.

>

>Dey, maybe you could just use VIRTIO_MAX_RX_PKTLEN here, like what you

>did in early versions.

>

>> >

>> >   2. Defining VLAN_TAG_SIZE is irrelevant if doing vlan offload.

>> > [Dey, Souvik] vlan offload is not mandatory. Se again still have

>> > vlan being sent up to

>the application. In that case we need to consider the vlan length in the Ethernet size.

>>

>> The code needs to handle both vlan offload (or not), correctly. You

>> are assuming the worst case here.

>

>I think we are fine here to assume worst case.

>

>> >

>> >   3. Virtio doesn't insert CRC, therefore CRC_LEN is irrelevant

>> > [Dey, Souvik] I am not sure of this. Mark commented earlier to consider this length too.

>Mark what do you suggest ?

>>

>> Actually, the thing that matters is the size of the merge rx buf header, not the CRC.

>

>Right.



My comments were based on my experience with DPDK ethdev PMDs - Stephen and Yuanhan have much more experience with virtio, so I'd go with their suggestion.



>

>            --yliu

>>

>> The patch is still buggy.

>>