Re: [PULL 07/20] virtio-net: Do not propagate ebpf-rss-fds errors

[Akihiko Odaki]

On 2024/06/06 16:14, Daniel P. Berrangé wrote:
> On Thu, Jun 06, 2024 at 05:14:20AM +0900, Akihiko Odaki wrote:
> > On 2024/06/05 19:23, Daniel P. Berrangé wrote:
> > > On Tue, Jun 04, 2024 at 03:37:42PM +0800, Jason Wang wrote:
> > > > From: Akihiko Odaki <akihiko.odaki@daynix.com>
> > > >
> > > > Propagating ebpf-rss-fds errors has several problems.
> > > >
> > > > First, it makes device realization fail and disables the fallback to the
> > > > conventional eBPF loading.
> > >
> > > AFAICT, this is not a bug - this is desired behaviour.
> > >
> > > If the user/mgmt app has told QEMU to use FDs it has passed
> > > in, then any failure to do this *MUST* be treated as a fatal
> > > error. Falling back to other codepaths is ignoring a direct
> > > user request.
> >
> > The FD options are more like an assistance rather than a request. When QEMU
> > does not have a permission to load eBPF programs, a user can get the eBPF
> > programs with the request-ebpf command of QMP, load it, and pass the FDs to
> > QEMU.
>
> That still doesn't alter the fact that if the user has chosen to pass FDs
> and QEMU fails to use them, it *MUST* report that error back to the user.

The user should be more interested in whether the eBPF functionality is 
successfully enabled or not, and that is irrelevant from whether the 
eBPF program is loaded by QEMU or someone else. It is being worked on 
with another patch series:
https://patchew.org/QEMU/20240428-auto-v1-0-7b012216a120@daynix.com/

Regards,
Akihiko Odaki