Re: [LSF/MM/BPF TOPIC][RESEND] Status of Rust in the block subsystem

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Mar 17, 2026 at 09:07:10AM +0100, Andreas Hindborg wrote:
> "Hannes Reinecke" <hare@suse.de> writes:
> 
> > On 3/17/26 00:51, Keith Busch wrote:
> >> On Wed, Mar 11, 2026 at 02:21:00PM +0100, Andreas Hindborg wrote:
> >>> As this topic was not selected for discussion at LSF, and I did not
> >>> receive an invitation for LSF this year, I propose that we discuss these
> >>> two topics on list.
> >>>
> >>> I do believe that these topics need to be discussed, and I would very
> >>> much appreciate your input.
> >>
> >> I can sympathise the difficulty of maintaining external modules.
> >>
> >> In terms of this being a reference driver, that implies some future
> >> hardware driver may leverage this for its development. Is there anything
> >> in mind at this point for production? If so, maybe that use case should
> >> take the lead. But either way, I think rust-nvme upstream inclusion
> >> would invite confusion. Once it's upstream, it's no longer a reference
> >> when distros and users turn it on.
> >>
> > I wholeheartedly agree.
> >
> > While I do see the original appeal to have a rust-nvme driver, having
> > one will just lead to confusion on all sides, especially for distros.
> > (Why is it there? should it be preferred to the original one? Do we
> > have to support both of them? Are there features missing in either
> > of these drivers?)
> > In general we are trying hard to avoid duplication in the linux kernel,
> > especially on the driver side. We constantly have to fight^Wargue
> > with driver vendors why duplicating existing drivers to support new
> > hardware is a bad idea, so we really should not start now just because
> > the driver is written in another language.
> > (That really might be giving vendors bad ideas :-)
> 
> I actually agree to some extent. But I do think we can get around most
> confusion with loud and clear documentation. We could make the driver
> not probe by default, requiring a configfs setting to probe. Or leave
> the PCI identifier table empty, so patching the driver is required to
> make it probe.
> 
> For me, the big benefit would be having the rust nvme driver as part of
> an allmodconfig or allyesconfig. That would prevent a ton of trouble.
> 
> We do plan to utilize the block infrastructure, but I think we are still
> quite a long way from sending anything. Keeping the rust nvme driver in
> tree till that point would prevent pci, dma, irq, etc. from developing
> in ways that would not support a block device use case. As an example,
> upstream Rust irq APIs are not actually able to support NVMe at the
> moment. They work fine for GPU drivers though. And I cannot go an fix
> them without a user. Same for DMA pool.
> 
> I could go and find some other piece of unsupported PCI hardware and
> write a driver for that, use that to keep the APIs in shape upstream.
> It's just a lot more work and the NVMe driver is already here and 90%
> ready.

This implies that there really is no "need" for these rust bindings at
all, if you don't know of, or are planning for, any real driver for
them.  So why have them at all?

For the PCI and driver core bindings, and the majority of the other ones
merged, we have real users (binder, nova-core, etc.) and so we are
willing to take them and keep them up to date.  For these block
bindings, why is it even worth it to have them around if there's never
going to be a real user?

thanks,

greg k-h