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Subject: Re: [PATCH] vdpa/mlx5: Use random MAC for the vdpa net instance
To:     "Michael S. Tsirkin" <mst@redhat.com>
Cc:     Eli Cohen <elic@nvidia.com>, Cindy Lu <lulu@redhat.com>,
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From:   Jason Wang <jasowang@redhat.com>
Message-ID: <eaaa5fb6-fd6a-200f-8457-d27f758f1c64@redhat.com>
Date:   Wed, 2 Dec 2020 21:33:19 +0800
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On 2020/12/2 下午9:07, Michael S. Tsirkin wrote:
>>>> Two questions here:
>>>> 1. Now we don't have support for control virtqueue. Yet, we must filter
>>>> packets based on MAC, what do you suggest to do here?
>>> How about an ioctl to pass the mac to the device?
>>> Maybe mirroring the control vq struct format ...
>> I think we'd better avoid such ad-hoc ioctls to make vhost-vDPA type
>> independent.
> Fundamentally this is about handling some VQs in QEMU, right?
> Maybe a generic ioctl along the lines of "CTRL_VQ" passing
> vq number and a command buffer from guest?
> Seems generic enough for you?
>

It looks to me you want to invent a synchronized API (or vDPA config 
ops) for submitting virtio descriptors.

Several issues I can think for this:

1) control vq allows the request to be handled asynchronously
2) we still need a way to isolate the DMA if there's a hardware 
virtqueue for the device that use DMA
3) new vDPA config operations need to be invented, new uAPI for 
vhost-vDPA, new virtio config ops for virtio-vDPA

It looks to me we can overcome 1) and 2) if we just stick to a virtqueue 
interface in vhost-vDPA as I proposed in [1]. For issue 3) it also 
requires much less work.

Thanks

[1] https://lkml.org/lkml/2020/9/23/1243