linux-kernel - Re: [PATCH v3] nvme-pci: Support shared tags across queues for Apple 2018 controllers

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Message-ID: <CACVXFVPbrXaAQe2C+13dNQSSL7f7gZ4QZ=W9vMpmmhJnxQMjew@mail.gmail.com>
Date:   Tue, 23 Jul 2019 09:36:40 +0800
From:   Ming Lei <tom.leiming@...il.com>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:     linux-nvme <linux-nvme@...ts.infradead.org>,
        Damien Le Moal <Damien.LeMoal@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Paul Pawlowski <paul@...rm.io>, Jens Axboe <axboe@...com>,
        Minwoo Im <minwoo.im.dev@...il.com>,
        Keith Busch <kbusch@...nel.org>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v3] nvme-pci: Support shared tags across queues for Apple
 2018 controllers

On Fri, Jul 19, 2019 at 1:31 PM Benjamin Herrenschmidt
<benh@...nel.crashing.org> wrote:
>
> From 8dcba2ef5b1466b023b88b4eca463b30de78d9eb Mon Sep 17 00:00:00 2001
> From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Date: Fri, 19 Jul 2019 15:03:06 +1000
> Subject:
>
> 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
>
> Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> ---
>
> Thanks Damien, reserved tags work and make this a lot simpler !
>
>  drivers/nvme/host/nvme.h |  5 +++++
>  drivers/nvme/host/pci.c  | 19 ++++++++++++++++++-
>  2 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> index ced0e0a7e039..8732da6df555 100644
> --- a/drivers/nvme/host/nvme.h
> +++ b/drivers/nvme/host/nvme.h
> @@ -102,6 +102,11 @@ enum nvme_quirks {
>          * Use non-standard 128 bytes SQEs.
>          */
>         NVME_QUIRK_128_BYTES_SQES               = (1 << 11),
> +
> +       /*
> +        * Prevent tag overlap between queues
> +        */
> +       NVME_QUIRK_SHARED_TAGS                  = (1 << 12),
>  };
>
>  /*
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index 7088971d4c42..fc74395a028b 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -2106,6 +2106,14 @@ static int nvme_setup_io_queues(struct nvme_dev *dev)
>         unsigned long size;
>
>         nr_io_queues = max_io_queues();
> +
> +       /*
> +        * If tags are shared with admin queue (Apple bug), then
> +        * make sure we only use one IO queue.
> +        */
> +       if (dev->ctrl.quirks & NVME_QUIRK_SHARED_TAGS)
> +               nr_io_queues = 1;
> +
>         result = nvme_set_queue_count(&dev->ctrl, &nr_io_queues);
>         if (result < 0)
>                 return result;
> @@ -2278,6 +2286,14 @@ static int nvme_dev_add(struct nvme_dev *dev)
>                 dev->tagset.flags = BLK_MQ_F_SHOULD_MERGE;
>                 dev->tagset.driver_data = dev;
>
> +               /*
> +                * Some Apple controllers requires tags to be unique
> +                * across admin and IO queue, so reserve the first 32
> +                * tags of the IO queue.
> +                */
> +               if (dev->ctrl.quirks & NVME_QUIRK_SHARED_TAGS)
> +                       dev->tagset.reserved_tags = NVME_AQ_DEPTH;
> +
>                 ret = blk_mq_alloc_tag_set(&dev->tagset);
>                 if (ret) {
>                         dev_warn(dev->ctrl.device,
> @@ -3057,7 +3073,8 @@ static const struct pci_device_id nvme_id_table[] = {
>         { PCI_DEVICE(PCI_VENDOR_ID_APPLE, 0x2003) },
>         { PCI_DEVICE(PCI_VENDOR_ID_APPLE, 0x2005),
>                 .driver_data = NVME_QUIRK_SINGLE_VECTOR |
> -                               NVME_QUIRK_128_BYTES_SQES },
> +                               NVME_QUIRK_128_BYTES_SQES |
> +                               NVME_QUIRK_SHARED_TAGS },
>         { 0, }
>  };
>  MODULE_DEVICE_TABLE(pci, nvme_id_table);

Looks fine for me:

Reviewed-by: Ming Lei <ming.lei@...hat.com>

Thanks,
Ming Lei