linux-kernel - Re: [PATCH v4 4/4] nvme-pci: Support shared tags across queues for Apple 2018 controllers

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Date:   Thu, 22 Aug 2019 02:29:21 +0200
From:   Christoph Hellwig <hch@....de>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:     linux-nvme@...ts.infradead.org, Sagi Grimberg <sagi@...mberg.me>,
        Jens Axboe <axboe@...com>, Keith Busch <keith.busch@...el.com>,
        Christoph Hellwig <hch@....de>, linux-kernel@...r.kernel.org,
        Paul Pawlowski <paul@...rm.io>
Subject: Re: [PATCH v4 4/4] nvme-pci: Support shared tags across queues for
 Apple 2018 controllers

On Wed, Aug 07, 2019 at 05:51:22PM +1000, Benjamin Herrenschmidt wrote:
> Another issue with the Apple T2 based 2018 controllers seem to be
> that they blow up (and shut the machine down) if there's a tag
> collision between the IO queue and the Admin queue.
> 
> My suspicion is that they use our tags for their internal tracking
> and don't mix them with the queue id. They also seem to not like
> when tags go beyond the IO queue depth, ie 128 tags.
> 
> This adds a quirk that marks tags 0..31 of the IO queue reserved

What a mess.  But given how widely available the macbooks are supporting
them makes sense:

Reviewed-by: Christoph Hellwig <hch@....de>