Re: [PATCH 0/3] add ifcvf driver

["Wang, Xiao W" <xiao.w.wang@intel.com>]

Hi Maxime,

> -----Original Message-----
> From: Maxime Coquelin [mailto:maxime.coquelin@redhat.com]
> Sent: Thursday, March 22, 2018 4:48 AM
> To: Wang, Xiao W <xiao.w.wang@intel.com>; dev@dpdk.org
> Cc: Wang, Zhihong <zhihong.wang@intel.com>; yliu@fridaylinux.org; Liang,
> Cunming <cunming.liang@intel.com>; Xu, Rosen <rosen.xu@intel.com>; Chen,
> Junjie J <junjie.j.chen@intel.com>; Daly, Dan <dan.daly@intel.com>
> Subject: Re: [PATCH 0/3] add ifcvf driver
> 
> Hi Xiao,
> 
> On 03/15/2018 05:49 PM, Wang, Xiao W wrote:
> > Hi Maxime,
> >
> >> -----Original Message-----
> >> From: Maxime Coquelin [mailto:maxime.coquelin@redhat.com]
> >> Sent: Sunday, March 11, 2018 2:24 AM
> >> To: Wang, Xiao W <xiao.w.wang@intel.com>; dev@dpdk.org
> >> Cc: Wang, Zhihong <zhihong.wang@intel.com>; yliu@fridaylinux.org; Liang,
> >> Cunming <cunming.liang@intel.com>; Xu, Rosen <rosen.xu@intel.com>;
> Chen,
> >> Junjie J <junjie.j.chen@intel.com>; Daly, Dan <dan.daly@intel.com>
> >> Subject: Re: [PATCH 0/3] add ifcvf driver
> >>
> >> Hi Xiao,
> >>
> >> On 03/10/2018 12:08 AM, Xiao Wang wrote:
> >>> This patch set has dependency on
> >> http://dpdk.org/dev/patchwork/patch/35635/
> >>> (vhost: support selective datapath);
> >>>
> >>> ifc VF is compatible with virtio vring operations, this driver implements
> >>> vDPA driver ops which configures ifc VF to be a vhost data path accelerator.
> >>>
> >>> ifcvf driver uses vdev as a control domain to manage ifc VFs that belong
> >>> to it. It registers vDPA device ops to vhost lib to enable these VFs to be
> >>> used as vhost data path accelerator.
> >>>
> >>> Live migration feature is supported by ifc VF and this driver enables
> >>> it based on vhost lib.
> >>>
> >>> vDPA needs to create different containers for different devices, thus this
> >>> patch set adds APIs in eal/vfio to support multiple container.
> >> Thanks for this! That will avoind having to duplicate these functions
> >> for every new offload driver.
> >>
> >>
> >>>
> >>> Junjie Chen (1):
> >>>     eal/vfio: add support for multiple container
> >>>
> >>> Xiao Wang (2):
> >>>     bus/pci: expose sysfs parsing API
> >>
> >> Still, I'm not convinced the offload device should be a virtual device.
> >> It is a real PCI device, why not having a new device type for offload
> >> devices, and let the device to be probed automatically by the existing
> >> device model?
> >
> > IFC VFs are generated from SRIOV, with the PF driven by kernel driver.
> > In DPDK we need to have something to represent PF, to register itself as
> > a vDPA engine, so a virtual device is used for this purpose.
> I went through the code, and something is not clear to me.
> 
> Why do we need to have a representation of the PF in DPDK?
> Why cannot we just bind at VF level?

1. With the vdev representation we could use it to talk to PF kernel driver to do flow configuration, we can implement
flow API on the vdev in future for this purpose. Using a vdev allows introducing this kind of control plane thing.

2. When port representor is ready, we would integrate it into ifcvf driver, then each VF will have a
Representor port. For now we don’t have port representor, so this patch set manages VF resource internally.

BRs,
Xiao