From: Hannes Reinecke <hare@suse.de>
To: Sagi Grimberg <sagi@grimberg.me>, Keith Busch <kbusch@kernel.org>
Cc: "Ewan D. Milne" <emilne@redhat.com>,
Daniel Wagner <dwagner@suse.de>,
linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
Jens Axboe <axboe@fb.com>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v2] nvme-tcp: Check if request has started before processing it
Date: Sun, 9 May 2021 13:30:35 +0200 [thread overview]
Message-ID: <8a396f94-ac33-6bea-8d70-ded0188eb98a@suse.de> (raw)
In-Reply-To: <7a45dd7f-842b-4282-909b-082b501abcdc@grimberg.me>
On 5/8/21 1:22 AM, Sagi Grimberg wrote:
>
>>>> Well, that would require a modification to the CQE specification, no?
>>>> fmds was not amused when I proposed that :-(
>>>
>>> Why would that require a modification to the CQE? it's just using say
>>> 4 msbits of the command_id to a running sequence...
>>
>> I think Hannes was under the impression that the counter proposal wasn't
>> part of the "command_id". The host can encode whatever it wants in that
>> value, and the controller just has to return the same value.
>
> Yea, maybe something like this?
> --
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index e6612971f4eb..7af48827ea56 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -1006,7 +1006,7 @@ blk_status_t nvme_setup_cmd(struct nvme_ns *ns,
> struct request *req)
> return BLK_STS_IOERR;
> }
>
> - cmd->common.command_id = req->tag;
> + cmd->common.command_id = nvme_cid(req);
> trace_nvme_setup_cmd(req, cmd);
> return ret;
> }
> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> index 05f31a2c64bb..96abfb0e2ddd 100644
> --- a/drivers/nvme/host/nvme.h
> +++ b/drivers/nvme/host/nvme.h
> @@ -158,6 +158,7 @@ enum nvme_quirks {
> struct nvme_request {
> struct nvme_command *cmd;
> union nvme_result result;
> + u8 genctr;
> u8 retries;
> u8 flags;
> u16 status;
> @@ -497,6 +498,48 @@ struct nvme_ctrl_ops {
> int (*get_address)(struct nvme_ctrl *ctrl, char *buf, int size);
> };
>
> +/*
> + * nvme command_id is constructed as such:
> + * | xxxx | xxxxxxxxxxxx |
> + * gen request tag
> + */
> +#define nvme_cid_install_genctr(gen) ((gen & 0xf) << 12)
> +#define nvme_genctr_from_cid(cid) ((cid & 0xf000) >> 12)
> +#define nvme_tag_from_cid(cid) (cid & 0xfff)
> +
That is a good idea, but we should ensure to limit the number of
commands a controller can request, too.
As per spec each controller can support a full 32 bit worth of requests,
and if we limit that arbitrarily from the stack we'll need to cap the
number of requests a controller or fabrics driver can request.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
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next prev parent reply other threads:[~2021-05-09 11:31 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-01 17:56 [PATCH v2] nvme-tcp: Check if request has started before processing it Daniel Wagner
2021-03-05 19:57 ` Sagi Grimberg
2021-03-11 9:43 ` Daniel Wagner
2021-03-15 17:16 ` Sagi Grimberg
2021-03-30 16:19 ` Ewan D. Milne
2021-03-30 17:34 ` Sagi Grimberg
2021-03-30 23:28 ` Keith Busch
2021-03-31 7:11 ` Hannes Reinecke
2021-03-31 21:01 ` Ewan D. Milne
2021-03-31 22:24 ` Sagi Grimberg
2021-04-01 6:20 ` Christoph Hellwig
2021-04-01 8:25 ` Sagi Grimberg
2021-03-31 22:37 ` Sagi Grimberg
2021-05-06 15:36 ` Hannes Reinecke
2021-05-07 20:26 ` Sagi Grimberg
2021-05-07 20:40 ` Keith Busch
2021-05-07 23:22 ` Sagi Grimberg
2021-05-08 0:03 ` Keith Busch
2021-05-09 11:30 ` Hannes Reinecke [this message]
2021-05-11 18:16 ` Sagi Grimberg
2021-05-17 14:58 ` Daniel Wagner
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