Re: [PATCH] nvme: associate stripe size quirk with D4512

[David Fugate <david.fugate@linux.intel.com>]

On Thu, 2020-07-02 at 14:48 -0700, Keith Busch wrote:
> On Thu, Jul 02, 2020 at 03:16:04PM -0600, David Fugate wrote:
> > Did hear from our D4512 team there are concerns with this drive
> > advertising itself as NVMe 1.2 compliant while also implementing
> > aspects of NVMe 1.3 such as NOIOB. Of course the Linux NVMe driver
> > does the right thing in terms of ignoring the drive-reported spec
> > compliance value in favor of feature detection. Can't be certain
> > that's the case with all other OSes and closed-source drivers
> > in particular.
> 
> I don't understand this concern. If a driver fails to detect a
> feature,
> then they're in the exact same situation as if the controller didn't
> implement it.

Imagine a less-enlightened NVMe driver which guards enablement of
features based *both* on the NVMe spec version the controller reports
as well as feature detection. In such cases, it wouldn't matter if a
drive implemented NOIOB (NVMe 1.3) if the controller advertises itself
as 1.2. E.g., same general type of version-checking logic as
implemented by nvme_report_ns_ids, but expanded to something that
actually *is* detectable as a feature. Linux does the right thing as
well as Intel-authored NVMe drivers I'm familiar with. Can't say this
for closed-source drivers though, and that was the concern given.


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