Re: RE: [virtio] [PATCH requirements 6/7] net-features: Add packet timestamp requirements

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

On Mon, 14 Aug 2023 13:06:03 +0000, Parav Pandit <parav@nvidia.com> wrote:
>
>
> > From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > Sent: Wednesday, August 9, 2023 2:06 PM
> >  struct vring_used_elem {
> >  	/* Index of start of used descriptor chain. */
> >  	__virtio32 id;
> >  	/* Total length of the descriptor chain which was used (written to) */
> >  	__virtio32 len;
> >
> > +	__virtio64 timestamp;
> >  };
> >
> >
> > Then, the existing devices can support this easily. If we introduce this by the
> > new desc structure, we can foresee that this function will not be implemented
> > by many existing machines. But this function is useful. So we want support this
> > by a simple way.
>
> This only works for split q.

YES.


> Packed q needs yet another format.
> And even after that we still have to live with other limitations listed in other requirements.

I would like some simple changes for the tx timestamp.

>
> Therefore its better to do the new desc definition one time which enables to optionally support timestamp, using single descriptor format.


I agree.

But we can have too. In addition to your plans, I would like to introduce a
simple method that can be used with existing machines.

Thanks.