RE: [PATCH v3 8/8] virtio-net: Describe RSS using receive queue handle

[Parav Pandit <parav@nvidia.com>]

> From: Michael S. Tsirkin <mst@redhat.com>
> Sent: Tuesday, March 21, 2023 6:17 PM

> > -Field \field{unclassified_queue} contains the 0-based index of -the
> > receive virtqueue to place unclassified packets in. Index 0 corresponds to
> receiveq1.
> > +\begin{lstlisting}
> > +le16 rq_handle;
> > +\end{lstlisting}
> > +
> > +\field{rq_handle} is a receive virtqueue handle. It is calculated as
> > +virtqueue number divided by two. For example a receive virtqueue
> > +handle value of 3 corresponds to virtqueue number 6 maps to receiveq4.
> > +
> > +Field \field{unclassified_queue} contains the receive queue handle
> > +\field{rq_handle} described above.
> 
> You dropped *which* queue this refers to.
>
Will add back.
 
> And it's still kind of complex and non-standard. E.g. what does \begin{lstlisting}
> le16 rq_handle;
> \end{lstlisting}
> mean exactly? Apparently nothing ...
> 
Why nothing, it is referenced further down.
Did you suggest moving before using it?
It was just fine to provide forward reference.

> I feel what we keep there is really the virtqueue number itself.
> Just stored in this strage format.
>
> And all this talk about handles kind of seems to add yet another term to learn.
> Where in fact all it is, is just a different way to store vqn.
> 
> So my idea was this: we say something like:
> 
> 
> \field{unclassified_queue} contains the virtqueue number of the receive queue
> to place unclassified packets in.
> \field{indirection_table} contains an array of virtqueue numbers of receive
> queues.
>
Above two lines are clearly confusing where virtqueue number describe in rest of the spec and above doesn't align to same notion.
So better to say field A contains the rq_handle and

struct rq_handle {
	le16 vqn_16_1: 15;
	le16 reserved : 1;
};

 
> Both \field{unclassified_queue} and \field{indirection_table} use the following
> format for the virtqueue numbers:
> \begin{lstlisting}
> struct rss_virtqueue_number {
It is really not any superior in term of cost of learning.

> 	le16 vqn_16_1 : 15; /* Bits 16 to 1 of the virtqueue number */
> 	le16 reserved : 1; /* Set to 0 */
I like the structure and reserved bit that enables to claim one bit for some unknown future use.
> }
> \end{lstlisting}
> for example, a value of 3 corresponds to virtqueue number 6 and maps to
> receiveq4.
> 
> 
> 
> and then everywhere else we just say it keeps a vq number, we already
> explained it is using this format once no need to repeat that.
>
I just prefer to rename it to rq_handle ( or at least other than virtqueue number) to distinguish it from rest of the virtqueue number.
 
> WDYT?