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Subject: Re: [PATCH V3 0/7] mdev based hardware virtio offloading support
To:     Stefan Hajnoczi <stefanha@gmail.com>
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References: <20191011081557.28302-1-jasowang@redhat.com>
 <20191014174946.GC5359@stefanha-x1.localdomain>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <6d12ad8f-8137-e07d-d735-da59a326e8ed@redhat.com>
Date:   Tue, 15 Oct 2019 11:37:17 +0800
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On 2019/10/15 上午1:49, Stefan Hajnoczi wrote:
> On Fri, Oct 11, 2019 at 04:15:50PM +0800, Jason Wang wrote:
>> There are hardware that can do virtio datapath offloading while having
>> its own control path. This path tries to implement a mdev based
>> unified API to support using kernel virtio driver to drive those
>> devices. This is done by introducing a new mdev transport for virtio
>> (virtio_mdev) and register itself as a new kind of mdev driver. Then
>> it provides a unified way for kernel virtio driver to talk with mdev
>> device implementation.
>>
>> Though the series only contains kernel driver support, the goal is to
>> make the transport generic enough to support userspace drivers. This
>> means vhost-mdev[1] could be built on top as well by resuing the
>> transport.
>>
>> A sample driver is also implemented which simulate a virito-net
>> loopback ethernet device on top of vringh + workqueue. This could be
>> used as a reference implementation for real hardware driver.
>>
>> Consider mdev framework only support VFIO device and driver right now,
>> this series also extend it to support other types. This is done
>> through introducing class id to the device and pairing it with
>> id_talbe claimed by the driver. On top, this seris also decouple
>> device specific parents ops out of the common ones.
> I was curious so I took a quick look and posted comments.
>
> I guess this driver runs inside the guest since it registers virtio
> devices?


It could run in either guest or host. But the main focus is to run in 
the host then we can use virtio drivers in containers.


>
> If this is used with physical PCI devices that support datapath
> offloading then how are physical devices presented to the guest without
> SR-IOV?


We will do control path meditation through vhost-mdev[1] and 
vhost-vfio[2]. Then we will present a full virtio compatible ethernet 
device for guest.

SR-IOV is not a must, any mdev device that implements the API defined in 
patch 5 can be used by this framework.

Thanks

[1] https://lkml.org/lkml/2019/9/26/15

[2] https://patchwork.ozlabs.org/cover/984763/


>
> Stefan