Re: [PATCH v6 11/21] virtio-net: Return an error when vhost cannot enable RSS

[Akihiko Odaki]

On 2023/10/30 21:14, Yuri Benditovich wrote:
> On Mon, Oct 30, 2023 at 7:14 AM Akihiko Odaki <akihiko.odaki@daynix.com 
> <mailto:akihiko.odaki@daynix.com>> wrote:
>
>     vhost requires eBPF for RSS. When eBPF is not available, virtio-net
>     implicitly disables RSS even if the user explicitly requests it. Return
>     an error instead of implicitly disabling RSS if RSS is requested but not
>     available.
>
>
> I think that suggesting RSS feature when in fact it is not available is 
> not a good idea, this rather desinforms the guest.
> Existing behavior (IMHO) makes more sense.
> We can extend this discussion if needed, of course.

This change is not to advertise RSS when it's not available; it instead 
reports an error to the user.

For example, think of the following command line:
qemu-system-x86_64 -device virtio-net,rss=on,netdev=n -netdev user,id=n

Before this change, it gives no error and the user will not know RSS is 
not available. With this change it now gives an error as follows:
qemu-system-x86_64: -device virtio-net,rss=on,netdev=n: Can't load eBPF RSS