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From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Max Gurtovoy <maxg@mellanox.com>
Cc: sagi@grimberg.me, vladimirk@mellanox.com, idanb@mellanox.com,
	israelr@mellanox.com, linux-nvme@lists.infradead.org,
	shlomin@mellanox.com, oren@mellanox.com,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	kbusch@kernel.org, hch@lst.de
Subject: Re: [PATCH] nvme-cli/fabrics: Add pi_enable param to connect cmd
Date: Fri, 08 Nov 2019 20:55:25 -0500
Message-ID: <yq14kzdx182.fsf@oracle.com> (raw)
In-Reply-To: <ed926da1-1466-edbd-6fa3-fb828bf455cc@mellanox.com> (Max Gurtovoy's message of "Thu, 7 Nov 2019 14:02:48 +0200")


Max,

> So iSER will create a signature resources for every capable device and
> connection without giving the user the possibility to distinguish
> between needed PI controllers and un-needed PI controllers.
>
> We don't have a format command in the fabrics so this is the best
> option we can think of for adding flexibility to users.
>
> I spoke with Christoph about the module param possibility and we both
> agreed it's not the way to go.
>
> Let me know if you have an idea that will enable flexibility to users.

The way it works in SCSI is that if a user wants to enable PI, they do
so when provision the device. So either a format for disk drives or by
selecting an option while creating a LUN in a storage array management
interface.

There are some knobs that can be twiddled on the initiator side to
enable/disable PI and/or DIX but these are meant for test or buggy
device workaround purposes. Not as a means for the user to select or
deselect the feature.

The user can decide on a per-device basis whether the block layer should
generate PI on write and verify on read. Those are the "proper" policy
knobs on the initiator side.

When an I/O request is received by the SCSI stack, we inspect it to
determine whether we need to allocate one or two scatterlists. If the
request has a bip attached, we'll allocate a separate scatterlist which
is then used to map the protection information before the I/O is
submitted to the device driver.

-- 
Martin K. Petersen	Oracle Linux Engineering

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Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-05 16:20 [PATCH 00/15] nvme-rdma/nvmet-rdma: Add metadata/T10-PI support Max Gurtovoy
2019-11-05 16:20 ` [PATCH] nvme-cli/fabrics: Add pi_enable param to connect cmd Max Gurtovoy
2019-11-07  2:36   ` Martin K. Petersen
2019-11-07 12:02     ` Max Gurtovoy
2019-11-09  1:55       ` Martin K. Petersen [this message]
2019-11-10  9:25         ` Max Gurtovoy
2019-11-12 17:47           ` Sagi Grimberg
2019-11-12 18:14             ` James Smart
2019-11-12 18:23               ` Sagi Grimberg
2019-11-05 16:20 ` [PATCH 01/15] nvme-fabrics: allow user enabling metadata/T10-PI support Max Gurtovoy
2019-11-12 17:48   ` Sagi Grimberg
2019-11-05 16:20 ` [PATCH 02/15] nvme: Fail __nvme_revalidate_disk in case of a spec violation Max Gurtovoy
2019-11-05 17:49   ` Christoph Hellwig
2019-11-12 17:52     ` Sagi Grimberg
2019-11-05 16:20 ` [PATCH 03/15] nvme: Introduce max_integrity_segments ctrl attribute Max Gurtovoy
2019-11-05 17:49   ` Christoph Hellwig
2019-11-12 17:53   ` Sagi Grimberg
2019-11-05 16:20 ` [PATCH 04/15] nvme: Inline nvme_ns_has_pi function Max Gurtovoy
2019-11-05 17:50   ` Christoph Hellwig
2019-11-05 16:20 ` [PATCH 05/15] nvme-rdma: Add metadata/T10-PI support Max Gurtovoy
2019-11-05 17:58   ` Christoph Hellwig
2019-11-12 18:22   ` Sagi Grimberg
2019-11-13 14:35     ` Max Gurtovoy
2019-11-14 23:57       ` Sagi Grimberg
2019-11-05 16:20 ` [PATCH 06/15] block: Introduce BIP_NOMAP_INTEGRITY bip_flag Max Gurtovoy
2019-11-05 17:52   ` Christoph Hellwig
2019-11-07  2:43   ` Martin K. Petersen
2019-11-07 13:29     ` Max Gurtovoy
2019-11-09  2:10       ` Martin K. Petersen
2019-11-12 10:40         ` Max Gurtovoy
2019-11-05 16:20 ` [PATCH 07/15] nvmet: Prepare metadata request Max Gurtovoy
2019-11-05 16:20 ` [PATCH 08/15] nvmet: Add metadata characteristics for a namespace Max Gurtovoy
2019-11-05 17:59   ` Christoph Hellwig
2019-11-12 18:38     ` Sagi Grimberg
2019-11-05 16:20 ` [PATCH 09/15] nvmet: Rename nvmet_rw_len to nvmet_rw_data_len Max Gurtovoy
2019-11-05 17:59   ` Christoph Hellwig
2019-11-12 18:39   ` Sagi Grimberg
2019-11-05 16:20 ` [PATCH 10/15] nvmet: Rename nvmet_check_data_len to nvmet_check_transfer_len Max Gurtovoy
2019-11-05 18:00   ` Christoph Hellwig
2019-11-12 18:43   ` Sagi Grimberg
2019-11-05 16:20 ` [PATCH 11/15] nvmet: Introduce nvmet_rw_prot_len and nvmet_ns_has_pi Max Gurtovoy
2019-11-05 18:00   ` Christoph Hellwig
2019-11-05 16:20 ` [PATCH 12/15] nvme: Add Metadata Capabilities enumerations Max Gurtovoy
2019-11-05 16:20 ` [PATCH 13/15] nvmet: Add metadata/T10-PI support Max Gurtovoy
2019-11-05 16:20 ` [PATCH 14/15] nvmet: Add metadata support for block devices Max Gurtovoy
2019-11-05 16:20 ` [PATCH 15/15] nvmet-rdma: Add metadata/T10-PI support Max Gurtovoy
2019-11-05 18:02   ` Christoph Hellwig
2019-11-07 13:43     ` Max Gurtovoy
2019-11-12 18:34   ` Sagi Grimberg
2019-11-13 13:56     ` Max Gurtovoy
2019-11-14 23:45       ` Sagi Grimberg

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