Re: RSS in virtio spec

[Yuri Benditovich <yuri.benditovich@daynix.com>]

Variant A

Index N corresponds to receiveqÂ(N+1)Â

On Wed, Mar 1, 2023 at 7:29âPM Michael S. Tsirkin <mst@redhat.com> wrote:

On Wed, Mar 01, 2023 at 07:17:19PM +0200, Yuri Benditovich wrote:
> HiÂMichael,
> I guess you mean https://github.com/oasis-tcs/virtio-spec/issues/135Â Is it
> correct?

No.

> I do not find words "queue index" in the respectiveÂdevice-types/net/
> description.tex
> It is stated in several places that "Index 0 corresponds to receiveq1"
> Sorry, but I do not exactly understand what is the issue? Can you please
> elaborate?Â
>
> Thanks,
> Yuri
>
> On Wed, Mar 1, 2023 at 12:28âPM Michael S. Tsirkin <mst@redhat.com> wrote:
>
>Â Â ÂHi!
>Â Â ÂCould you pls comment on the issue of "queue index" in the
>Â Â Ârss indirection table? What is ment by that?
>
>Â Â ÂThanks!
>Â Â Â--
>Â Â ÂMST
>

These two:


Field \field{unclassified_queue} contains the 0-based index of
the receive virtqueue to place unclassified packets in. Index 0 corresponds to receiveq1.


...

Field \field{indirection_table} contains an array of 0-based indices of receive virtqueus. Index 0 corresponds to receiveq1.



BTW there's a typo virtqueus :)

More importantly:

What does "0-based indices of receive virtqueus" mean?

Sure 0 is receiveq1. But how does one refer to receiveq3 ?

A. we take the number after "q" and subtract 1. Thus receiveq2 -> 1. receiveq3 -> 2
 Âmax index is 0x7ffe higher indices are unused.
B. we take the index of the VQ. Thus receiveq2 -> 2, receiveq3 -> 4
 Âmax index is 0xfffc and indices are even, odd indices would
 Âcorrespond to transmitq and thus are unused for RSS.