linux-kernel - Re: [PATCH v2 3/3] nvme: prevent ioq creation for discovery controllers

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Message-ID: <53116592-1949-4fdf-8935-e324b8779900@suse.de>
Date: Thu, 3 Jul 2025 11:42:24 +0200
From: Hannes Reinecke <hare@...e.de>
To: Kamaljit Singh <kamaljit.singh1@....com>, kbusch@...nel.org,
 axboe@...nel.dk, hch@....de, sagi@...mberg.me,
 linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: cassel@...nel.org, dlemoal@...nel.org
Subject: Re: [PATCH v2 3/3] nvme: prevent ioq creation for discovery
 controllers

On 7/2/25 02:58, Kamaljit Singh wrote:
> Prevent ioq creation for discovery-controllers as the spec prohibits
> them, similarly to the administrative controllers.
> 
> Reference: NVMe Base rev 2.2, sec 3.1.3.4, fig 28.
> 
While this might be true, we already deal with discovery controllers
just fine, and never had issues with I/O queues being created.
Presumably because discovery controllers never exposed I/O queues
in the first place.

Which also means that admin controllers should work already if they
would not expose I/O queues.

We _might_ reduce the number of queues to '1' in nvme_set_queue_count(),
but then we should issue a warning here as this would be a configuration
error on the target side.

'Prohibited' cuts both ways; the host shouldn't ask for it and the
controller shouldn't advertise it...

Or that's at least my reading. Might be worthwhile clarifying this
at FMDS.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@...e.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich