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

Dey, Souvik sodey at sonusnet.com
Tue Sep 27 17:41:07 CEST 2016


Hi All,
	Any further updates/comments on this ?

--
Regards,
Souvik

-----Original Message-----
From: Yuanhan Liu [mailto:yuanhan.liu at linux.intel.com] 
Sent: Sunday, September 25, 2016 11:21 PM
To: Stephen Hemminger <stephen at networkplumber.org>
Cc: Dey, Souvik <sodey at sonusnet.com>; Kavanagh, Mark B <mark.b.kavanagh at intel.com>; dev at dpdk.org
Subject: Re: [PATCH v6] net/virtio: add set_mtu in virtio

Hi Stephen,

Are you okay with this change?

	--yliu

On Fri, Sep 23, 2016 at 03:17:37PM +0000, Dey, Souvik wrote:
> 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> 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>
> 
> >> > Cc: mark.b.kavanagh at intel.com; yuanhan.liu at linux.intel.com;
> 
> >> > 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> 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.
> 
> >> 
> 


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