Re: [PATCH v8 5/5] selftests/io_uring: add a bpf io_uring selftest

[Ming Lei <ming.lei@redhat.com>]

On Tue, Feb 24, 2026 at 12:30 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
>
> On 2/23/26 15:23, Ming Lei wrote:
> > On Sat, Feb 21, 2026 at 6:35 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
> >>
> >> On 2/20/26 17:45, Alexei Starovoitov wrote:
> >>> On Fri, Feb 20, 2026 at 3:41 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
> >>>>
> >>>> I had such examples, but selftests is not the best place for that.
> >>>> It can use abstractions, and I want to make them reusable instead
> >>>> of people copy-pasting from selftests.
> >>>
> >>> Sure, but please still post them as extra patches so it's easier
> >>> to see what's the end result.
> >>>
> >>> Also please reply to that thread:
> >>> https://lore.kernel.org/bpf/CALTww28QMg=YXqKWpWLZrLO+xiqOe3LGyput8dx68-dnQsxg=g@mail.gmail.com/
> >>>
> >>> It's not clear to me whether your io_uring+bpf setup will work
> >>> for Xiao's use case.
> >>> I don't think we need 2 ways of doing it.
> >>
> >> We discussed this with Ming on the list before, that's one of the use
> >> cases I target as well, there is no reason why it shouldn't work. The
> >> difference is that this approach gives a flexible framework for
> >> extensibility and covers a good bunch of other needs, which is exactly
> >> the reason I moved from a BPF opcode approach, while Ming's proposal is
> >> more specific but argued to be a way easier to plug into ublk servers.
> >> If you ask me, we need a solution that covers a broader spectrum of
> >> use cases, but I guess it all can be argued in either way.
> >
> > One big drawback of  Pavel's approach is that it needs a totally
> > different userspace
> > implementation for using BPF, which is just hard to use in existing
> > io_uring applications.
>
> Not really, it depends on how you write it. If you need to rewrite CQ

I meant SQE has to be allocated & built in bpf prog, then it is inevitable
to move application logic into bpf prog.

If the logic is complicated, it is one big thing.

raid5 is a great example with complicated fast io code path, I'd suggest someone
or Xiao or Caleb, try it. Compare your approach to the bpf opcode and draw
some useful conclusions.  Code should be more convincing.

For bpf opcode approach I believe Xiao has already built an example.


Thanks,
Ming