Re: [PATCH v2] nvme: reserve a keep-alive admin tag for all transports

[Keith Busch <kbusch@kernel.org>]

On Thu, May 21, 2026 at 10:25:49AM +0200, Christoph Hellwig wrote:
> On Wed, May 20, 2026 at 02:26:13PM -0600, Keith Busch wrote:
> > I am skeptical anyone would produce a PCIe device that supports it, but
> > let's say someone does: what is the use case motivating enabling this
> > optional feature in this driver? If it's just because the option is
> > there, then I think we can just reject the user command submitting the
> > feature for PCIe transports, like I earlier suggested. Requiring an
> > active command will just harm idle power states.
> 
> I don't think that's quite the point.  We'd have to add special
> filtering to fix the reproducer.  Compared to that just reserving
> a tag and officially supporting the feature is much easier and a much
> better story.

This command is already special since we filter for it on the completion
side. We may want to selectively filter other Set Feature commands too.
For example, we don't want user space turning on Host Dispersed
Namespace Support, because this driver is not going to correctly react
to that one either.