Re: [PATCH] PCI: Add Intel remapped NVMe device support

[Christoph Hellwig <hch@lst.de>]

On Wed, Jun 12, 2019 at 08:32:46AM -0600, Keith Busch wrote:
> On Mon, Jun 10, 2019 at 8:46 PM Daniel Drake <drake@endlessm.com> wrote:
> > What's the specific problem that you see here?
> 
> Performance. Have you had a chance to benchmark these storage devices
> comparing legacy vs MSI interrupts? I don't think anyone would chose
> the slower one on purpose. These platforms have an option to disable
> raid mode, so the kernel's current recommendation should be the user's
> best option.

And it isn't just performance.  I really don't understand how

 a) quirks on the PCI ID
 b) reset handling, including the PCI device removal as the last
    escalation step
 c) SR-IOV VFs and their management
 d) power management

and probably various other bits I didn't even think of are going to
work.

So until we get very clear and good documentation from Intel on that
I don't think any form of upstream support will fly.  And given that
Dan who submitted the original patch can't even talk about this thing
any more and apparently got a gag order doesn't really give me confidence
any of this will ever work.