Re: [PATCH v3 2/4] net/virtio: skip device probe in vdpa mode

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

Hi Thomas,

> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas@monjalon.net]
> Sent: Saturday, March 31, 2018 9:16 PM
> To: Maxime Coquelin <maxime.coquelin@redhat.com>
> Cc: Wang, Xiao W <xiao.w.wang@intel.com>; Yigit, Ferruh
> <ferruh.yigit@intel.com>; dev@dpdk.org; Wang, Zhihong
> <zhihong.wang@intel.com>; yliu@fridaylinux.org; Tan, Jianfeng
> <jianfeng.tan@intel.com>; Bie, Tiwei <tiwei.bie@intel.com>; Liang, Cunming
> <cunming.liang@intel.com>; Daly, Dan <dan.daly@intel.com>;
> gaetan.rivet@6wind.com; Burakov, Anatoly <anatoly.burakov@intel.com>
> Subject: Re: [PATCH v3 2/4] net/virtio: skip device probe in vdpa mode
> 
> Hi,
> 
> 31/03/2018 13:13, Maxime Coquelin:
> > On 03/31/2018 04:29 AM, Xiao Wang wrote:
> > > If we want a virtio device to work in vDPA (vhost data path acceleration)
> > > mode, we could add a "vdpa=1" devarg for this device to specify the mode.
> > >
> > > This patch let virtio pmd skip device probe when detecting this parameter.
> >
> > As we discussed, I would prefer a generic solution at EAL level.
> 
> Please could you explain the requirement and the context?
> Can we use RTE_ETH_DEV_DEFERRED state and device ownership?
> 
> Without knowing what's behind, I would say that a PMD should
> never skip a device by itself, but let other entities decide
> what to do with the probed device (thanks to probe notifications).
> 

IFCVF's vendor ID and device ID are the same as that of virtio net pci device,
with its specific subsystem vendor ID and device ID. The context is
IFCVF can be driven by both virtio pmd and IFCVF driver, so we add this
devarg to specify if we want the device to work in vDPA mode or not.
For vdpa-mode IFCVF, virtio pmd should not take over it, so we let it skip.

BRs,
Xiao