Re: [dpdk-dev] [RFC v2 2/2] net/vhost_dma: add vHost DMA driver

["Hu, Jiayu" <jiayu.hu@intel.com>]

Hi Maxime,

Replies are inline.

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Tuesday, December 17, 2019 4:27 PM
> To: Hu, Jiayu <jiayu.hu@intel.com>; dev@dpdk.org
> Cc: Bie, Tiwei <tiwei.bie@intel.com>; Wang, Zhihong
> <zhihong.wang@intel.com>; Richardson, Bruce
> <bruce.richardson@intel.com>
> Subject: Re: [RFC v2 2/2] net/vhost_dma: add vHost DMA driver
> 
> Hi Jiayu,
> > Here is an example.
> > $ ./testpmd -c f -n 4 \
> > --vdev
> 'dma_vhost0,iface=/tmp/sock0,queues=1,dmas=txq0@00:04.0,client=0'
> 
> dma_vhost0 is not a good name, you have to mention it is net specific.
> 
> Is there a tool to list available DMA engines?

Yes, you can use dpdk-devbind.py to list available DMA engines.

> 
> >
> > Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
> > ---
> >  config/common_base                                 |    2 +
> >  config/common_linux                                |    1 +
> >  drivers/Makefile                                   |    2 +-
> >  drivers/net/Makefile                               |    1 +
> >  drivers/net/vhost_dma/Makefile                     |   31 +
> >  drivers/net/vhost_dma/eth_vhost.c                  | 1495
> ++++++++++++++++++++
> >  drivers/net/vhost_dma/eth_vhost.h                  |  264 ++++
> >  drivers/net/vhost_dma/internal.h                   |  225 +++
> >  .../net/vhost_dma/rte_pmd_vhost_dma_version.map    |    4 +
> >  drivers/net/vhost_dma/virtio_net.c                 | 1234 ++++++++++++++++
> >  mk/rte.app.mk                                      |    1 +
> >  11 files changed, 3259 insertions(+), 1 deletion(-)
> >  create mode 100644 drivers/net/vhost_dma/Makefile
> >  create mode 100644 drivers/net/vhost_dma/eth_vhost.c
> >  create mode 100644 drivers/net/vhost_dma/eth_vhost.h
> >  create mode 100644 drivers/net/vhost_dma/internal.h
> >  create mode 100644
> drivers/net/vhost_dma/rte_pmd_vhost_dma_version.map
> >  create mode 100644 drivers/net/vhost_dma/virtio_net.c
> 
> You need to add Meson support.

Will add meson build later.

> 
> 
> More generally, I have been through the series and I'm not sure having a
> dedicated PMD driver for this is a good idea due to all the code
> duplication it implies.
> 
> I understand it has been done this way to avoid impacting the pure SW
> datapath implementation. But I'm sure the series could be reduced to a
> few hundred of lines if it was integrated in vhost-user library.
> Moreover, your series does not support packed ring, so it means even
> more code would need to be duplicated in the end.

Yes, providing a new PMD is to avoid impacting vhost library. To avoid
too much duplicated code, we can just provide a separate DMA accelerated
data-path in vhost-user PMD, rather than introducing a new PMD. How
do you think?

Thanks,
Jiayu
> 
> What do you think?
> 
> Thanks,
> Maxime