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	id B6F1168BEB; Wed, 10 Jun 2026 07:11:46 +0200 (CEST)
Date: Wed, 10 Jun 2026 07:11:46 +0200
From: Christoph Hellwig <hch@lst.de>
To: Nick Chan <towinchenmi@gmail.com>
Cc: Sven Peter <sven@kernel.org>, Janne Grunau <j@jannau.net>,
	Neal Gompa <neal@gompa.dev>, Keith Busch <kbusch@kernel.org>,
	Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
	Sagi Grimberg <sagi@grimberg.me>, asahi@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org,
	linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org
Subject: Re: [PATCH 1/2] nvme-apple: Only limit admin queue tag space when
 with Linear SQ is present
Message-ID: <20260610051146.GA559@lst.de>
References: <20260606-prevent-tag-collision-t8015-v1-0-93ccf4eca550@gmail.com> <20260606-prevent-tag-collision-t8015-v1-1-93ccf4eca550@gmail.com>
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User-Agent: Mutt/1.5.17 (2007-11-01)

On Sat, Jun 06, 2026 at 09:25:25PM +0800, Nick Chan wrote:
> Apple NVMe controllers require tags of pending commands to not be shared
> across admin and IO queues. However, on Apple A11 without linear SQ, it is
> not possible for either queue to skip over some tags and must go from 0 to
> the configured maximum before wrapping around.
> 
> As a result, in order to prevent tag collision, dynamic tag reservation
> while a command is in-flight becomes necessary. In this context, there is
> no reason to limit the admin queue's tag space, as it is not helpful in
> preventing tag collision.

I'm not really into these Apple specific, but what does
"dynamic tag reservation" mean here?