linux-kernel - Re: [PATCH] nvme: Inform controller of doorbell config before unquiescing IO queues

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Message-ID: <ZZ7knJGSVx8hWvaW@kbusch-mbp>
Date: Wed, 10 Jan 2024 11:40:28 -0700
From: Keith Busch <kbusch@...nel.org>
To: William Butler <wab@...gle.com>
Cc: Pavel Emelyanov <xemul@...nvz.org>, Christoph Hellwig <hch@....de>,
	Sagi Grimberg <sagi@...mberg.me>, Jens Axboe <axboe@...nel.dk>,
	linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org
Subject: Re: [PATCH] nvme: Inform controller of doorbell config before
 unquiescing IO queues

On Wed, Jan 10, 2024 at 06:28:55PM +0000, William Butler wrote:
> During resets, if queues are unquiesced first, then the host can submit
> IOs to the controller using shadow doorbell logic but the controller
> won't be aware. This can lead to necessary MMIO doorbells from being
> not issued, causing requests to be delayed and timed-out.

Good catch. I guess we wouldn't normally expect any requests to be in
queue at this point, but plenty of reasons it could happen.

Applied to nvme-6.8 with a slightly updated title to match the local
conventions.