netdev - Re: [PATCH 5/5] vdpasim: vDPA device simulator

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Date:   Fri, 17 Jan 2020 14:10:24 +0000
From:   Jason Gunthorpe <jgg@...lanox.com>
To:     Jason Wang <jasowang@...hat.com>
CC:     "mst@...hat.com" <mst@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
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        Parav Pandit <parav@...lanox.com>,
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Subject: Re: [PATCH 5/5] vdpasim: vDPA device simulator

On Fri, Jan 17, 2020 at 05:32:39PM +0800, Jason Wang wrote:
> 
> On 2020/1/16 下午11:47, Jason Gunthorpe wrote:
> > On Thu, Jan 16, 2020 at 08:42:31PM +0800, Jason Wang wrote:
> > > This patch implements a software vDPA networking device. The datapath
> > > is implemented through vringh and workqueue. The device has an on-chip
> > > IOMMU which translates IOVA to PA. For kernel virtio drivers, vDPA
> > > simulator driver provides dma_ops. For vhost driers, set_map() methods
> > > of vdpa_config_ops is implemented to accept mappings from vhost.
> > > 
> > > A sysfs based management interface is implemented, devices are
> > > created and removed through:
> > > 
> > > /sys/devices/virtual/vdpa_simulator/netdev/{create|remove}
> > This is very gross, creating a class just to get a create/remove and
> > then not using the class for anything else? Yuk.
> 
> 
> It includes more information, e.g the devices and the link from vdpa_sim
> device and vdpa device.

I feel like regardless of how the device is created there should be a
consistent virtio centric management for post-creation tasks, such as
introspection and destruction

A virto struct device should already have back pointers to it's parent
device, which should be enough to discover the vdpa_sim, none of the
extra sysfs munging should be needed.

> > > Netlink based lifecycle management could be implemented for vDPA
> > > simulator as well.
> > This is just begging for a netlink based approach.
> > 
> > Certainly netlink driven removal should be an agreeable standard for
> > all devices, I think.
> 
> 
> Well, I think Parav had some proposals during the discussion of mdev
> approach. But I'm not sure if he had any RFC codes for me to integrate it
> into vdpasim.
>
> Or do you want me to propose the netlink API? If yes, would you prefer to a
> new virtio dedicated one or be a subset of devlink?

Well, lets see what feed back Parav has

Jason