Re: [PATCH 1/3] nvme: add ABI documentation for host sysfs interfaces

On 7/2/26 5:48 AM, Guixin Liu wrote:
> Add Documentation/ABI/testing/sysfs-nvme documenting all NVMe host
> sysfs attributes, covering controller attributes under
> /sys/class/nvme/nvmeX/, namespace attributes under
> /sys/block/nvmeXnY/, and subsystem attributes under
> /sys/class/nvme-subsystem/nvme-subsysX/.
> 
> Each entry has been traced to its original introducing commit to
> provide accurate Date, KernelVersion, and Contact information.
> 
> Signed-off-by: Guixin Liu <[email protected]>
> ---
>   Documentation/ABI/testing/sysfs-nvme | 444 ++++++++++++++++++++++++++-
>   1 file changed, 434 insertions(+), 10 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-nvme b/Documentation/ABI/testing/sysfs-nvme
> index 499d5f843cd4..079561601acd 100644
> --- a/Documentation/ABI/testing/sysfs-nvme
> +++ b/Documentation/ABI/testing/sysfs-nvme
> @@ -1,13 +1,437 @@
> -What:		/sys/devices/virtual/nvme-fabrics/ctl/.../tls_configured_key
> +What:		/sys/class/nvme/nvmeX/model
> +What:		/sys/class/nvme/nvmeX/serial
> +What:		/sys/class/nvme/nvmeX/firmware_rev
> +Date:		January 2016
> +KernelVersion:	4.5
> +Contact:	Keith Busch <[email protected]>
> +Description:
> +		Shows the model, serial number, or firmware revision string
> +		of the NVMe controller, as reported in the Identify
> +		Controller data structure.
> +
> +What:		/sys/class/nvme/nvmeX/reset_controller
> +Date:		November 2015
> +KernelVersion:	4.5
> +Contact:	Christoph Hellwig <[email protected]>
> +Description:
> +		Write-only. Writing any value triggers a synchronous
> +		controller reset.
> +
> +What:		/sys/block/nvmeXnY/uuid
> +What:		/sys/block/nvmeXnY/eui
> +What:		/sys/block/nvmeXnY/nsid
> +Date:		December 2015
> +KernelVersion:	4.5
> +Contact:	Keith Busch <[email protected]>
> +Description:
> +		Namespace identification attributes.
> +
> +		uuid: Shows the UUID for this namespace. Falls back to
> +		showing the NGUID for backward compatibility. Hidden if
> +		both are all zeros.
> +
> +		eui: Shows the IEEE Extended Unique Identifier (EUI-64).
> +		Hidden if all zeros.
> +
> +		nsid: Shows the namespace identifier (NSID).
> +
> +What:		/sys/class/nvme/nvmeX/cntlid
> +Date:		February 2016
> +KernelVersion:	4.6
> +Contact:	Ming Lin <[email protected]>
> +Description:
> +		Shows the controller identifier assigned by the NVMe
> +		subsystem.
> +
> +What:		/sys/block/nvmeXnY/wwid
> +Date:		February 2016
> +KernelVersion:	4.6
> +Contact:	Keith Busch <[email protected]>
> +Description:
> +		Shows the World Wide Identifier for this namespace. The
> +		format depends on available identifiers (in priority
> +		order): "uuid.{UUID}", "eui.{NGUID}", "eui.{EUI64}", or
> +		"nvme.{VID}-{SERIAL}-{MODEL}-{NSID}".
> +
> +What:		/sys/class/nvme/nvmeX/rescan_controller
> +Date:		April 2016
> +KernelVersion:	4.7
> +Contact:	Keith Busch <[email protected]>
> +Description:
> +		Write-only. Writing any value triggers a namespace rescan
> +		on this controller.
> +
> +What:		/sys/class/nvme/nvmeX/transport
> +What:		/sys/class/nvme/nvmeX/subsysnqn
> +What:		/sys/class/nvme/nvmeX/address
> +What:		/sys/class/nvme/nvmeX/delete_controller
> +What:		/sys/class/nvme/nvmeX/reconnect_delay
> +What:		/sys/class/nvme/nvmeX/ctrl_loss_tmo
> +Date:		June 2016
> +KernelVersion:	4.8
> +Contact:	Ming Lin <[email protected]>
> +Description:
> +		Fabrics controller attributes added with NVMe-oF support.
> +
> +		transport: Shows the transport type string. Possible values:
> +		"pcie", "tcp", "rdma", "fc", "loop".
> +
> +		subsysnqn: Shows the NVMe Qualified Name (NQN) of the
> +		subsystem this controller belongs to.
> +
> +		address: Shows the transport-specific address string. Only
> +		available for fabrics controllers.
> +
> +		delete_controller: Write-only. Triggers deletion of this
> +		fabrics controller.
> +
> +		reconnect_delay: Shows or sets the reconnect delay in
> +		seconds. Reading returns the delay value, or "off" if
> +		disabled.
> +
> +		ctrl_loss_tmo: Shows or sets the controller loss timeout in
> +		seconds. Reading returns the timeout value, or "off" if
> +		infinite reconnects are allowed. Writing a negative value
> +		disables the timeout.
> +
> +What:		/sys/class/nvme/nvmeX/cmb
> +Date:		October 2016
> +KernelVersion:	4.9
> +Contact:	Stephen Bates <[email protected]>
> +Description:
> +		Shows the Controller Memory Buffer (CMB) register values
> +		in format "cmbloc : 0x%08x\ncmbsz  : 0x%08x\n". Only
> +		visible when the controller has a CMB (cmbsz != 0).
> +		PCI transport only.
> +
> +What:		/sys/class/nvme/nvmeX/state
> +Date:		November 2016
> +KernelVersion:	4.11
> +Contact:	Sagi Grimberg <[email protected]>
> +Description:
> +		Shows the current state of the controller. Possible values:
> +		"new", "live", "resetting", "connecting", "deleting",
> +		"deleting (no IO)", "dead".
> +
> +What:		/sys/block/nvmeXnY/nguid
> +Date:		June 2017
> +KernelVersion:	4.13
> +Contact:	Johannes Thumshirn <[email protected]>
> +Description:
> +		Shows the Namespace Globally Unique Identifier (NGUID).
> +		Hidden if the NGUID is all zeros.
> +
> +What:		/sys/class/nvme-subsystem/nvme-subsysX/model
> +What:		/sys/class/nvme-subsystem/nvme-subsysX/serial
> +What:		/sys/class/nvme-subsystem/nvme-subsysX/firmware_rev
> +What:		/sys/class/nvme-subsystem/nvme-subsysX/subsysnqn
> +Date:		November 2017
> +KernelVersion:	4.15
> +Contact:	Hannes Reinecke <[email protected]>
> +Description:
> +		Shows the model, serial number, firmware revision, or NQN
> +		of the NVMe subsystem.
> +
> +What:		/sys/block/nvmeXnY/ana_grpid
> +What:		/sys/block/nvmeXnY/ana_state
> +Date:		May 2018
> +KernelVersion:	4.19
> +Contact:	Christoph Hellwig <[email protected]>
> +Description:
> +		ana_grpid: Shows the ANA Group ID for this per-path
> +		namespace device.
> +
> +		ana_state: Shows the ANA state. Possible values:
> +		"optimized", "non-optimized", "inaccessible",
> +		"persistent-loss", "change".
> +
> +		Only visible on per-path devices (not multipath head) when
> +		the controller supports ANA. Requires CONFIG_NVME_MULTIPATH.
> +
> +What:		/sys/class/nvme/nvmeX/numa_node
> +Date:		November 2018
> +KernelVersion:	5.0
> +Contact:	Hannes Reinecke <[email protected]>
> +Description:
> +		Shows the NUMA node the controller is attached to.
> +
> +What:		/sys/class/nvme-subsystem/nvme-subsysX/iopolicy
> +Date:		February 2019
> +KernelVersion:	5.1
> +Contact:	Hannes Reinecke <[email protected]>
> +Description:
> +		Shows or sets the multipath I/O path selection policy for
> +		this subsystem. Accepted values: "numa", "round-robin",
> +		"queue-depth". Changing the policy clears all current path
> +		selections. Only available when CONFIG_NVME_MULTIPATH is
> +		enabled.
> +
> +What:		/sys/class/nvme/nvmeX/queue_count
> +What:		/sys/class/nvme/nvmeX/sqsize
> +Date:		September 2019
> +KernelVersion:	5.4
> +Contact:	James Smart <[email protected]>
> +Description:
> +		queue_count: Shows the total number of queues (admin + I/O)
> +		for this controller.
> +
> +		sqsize: Shows the submission queue size for this controller.
> +
> +What:		/sys/class/nvme/nvmeX/hostnqn
> +What:		/sys/class/nvme/nvmeX/hostid
> +Date:		February 2020
> +KernelVersion:	5.7
> +Contact:	Sagi Grimberg <[email protected]>
> +Description:
> +		hostnqn: Shows the host NQN used by this fabrics controller.
> +
> +		hostid: Shows the host identifier (UUID format) used by this
> +		fabrics controller.
> +
> +		Only available for fabrics controllers.
> +
> +What:		/sys/class/nvme/nvmeX/fast_io_fail_tmo
> +Date:		November 2020
> +KernelVersion:	5.11
> +Contact:	Victor Gladkov <[email protected]>
> +Description:
> +		Shows or sets the fast I/O fail timeout in seconds. Reading
> +		returns the timeout value, or "off" if disabled. Writing a
> +		negative value disables the fast I/O fail. Only available
> +		for fabrics controllers.
> +
> +What:		/sys/class/nvme/nvmeX/kato
> +Date:		April 2021
> +KernelVersion:	5.13
> +Contact:	Hannes Reinecke <[email protected]>
> +Description:
> +		Shows the Keep Alive Timeout value in milliseconds for
> +		this controller.
> +
> +What:		/sys/class/nvme/nvmeX/cmbloc
> +What:		/sys/class/nvme/nvmeX/cmbsz
> +What:		/sys/class/nvme/nvmeX/hmb
> +Date:		July 2021
> +KernelVersion:	5.15
> +Contact:	Keith Busch <[email protected]>
> +Description:
> +		cmbloc: Shows the CMBLOC register value.
> +
> +		cmbsz: Shows the CMBSZ register value.
> +
> +		cmbloc and cmbsz are only visible when the controller has
> +		a CMB. PCI transport only.
> +
> +		hmb: Shows or sets whether the Host Memory Buffer (HMB) is
> +		enabled. Reading returns 1 (enabled) or 0 (disabled).
> +		Writing 1 enables HMB; writing 0 disables it. Only
> +		visible when the controller supports HMB (hmpre != 0).
> +		PCI transport only.
> +
> +What:		/sys/class/nvme-subsystem/nvme-subsysX/subsystype
> +Date:		September 2021
> +KernelVersion:	5.16
> +Contact:	Hannes Reinecke <[email protected]>
> +Description:
> +		Shows the subsystem type. Possible values: "discovery",
> +		"nvm", "reserved".
> +
> +What:		/sys/class/nvme/nvmeX/cntrltype
> +What:		/sys/class/nvme/nvmeX/dctype
> +Date:		February 2022
> +KernelVersion:	5.18
> +Contact:	Martin Belanger <[email protected]>
> +Description:
> +		cntrltype: Shows the controller type. Possible values: "io",
> +		"discovery", "admin", "reserved".
> +
> +		dctype: Shows the discovery controller type. Possible values:
> +		"none", "ddc", "cdc", "reserved".
> +
> +What:		/sys/class/nvme/nvmeX/dhchap_secret
> +What:		/sys/class/nvme/nvmeX/dhchap_ctrl_secret
> +Date:		June 2022
> +KernelVersion:	6.0
> +Contact:	Hannes Reinecke <[email protected]>
> +Description:
> +		dhchap_secret: Shows or sets the host DH-HMAC-CHAP secret
> +		for this controller. Reading returns "none" if not set.
> +		Writing must use the "DHHC-1:" key format and triggers
> +		re-authentication.
> +
> +		dhchap_ctrl_secret: Shows or sets the controller
> +		DH-HMAC-CHAP secret for bidirectional authentication.
> +		Same format as dhchap_secret.
> +
> +		Only available when CONFIG_NVME_HOST_AUTH is enabled and
> +		for fabrics controllers.
> +
> +What:		/sys/class/nvme/nvmeX/tls_key
> +Date:		August 2023
> +KernelVersion:	6.7
> +Contact:	Hannes Reinecke <[email protected]>
> +Description:
> +		Shows the serial of the currently active TLS PSK as hex.
> +		Returns empty if no TLS key is active. Only available for
> +		TCP controllers with TLS or secure concatenation enabled
> +		(CONFIG_NVME_TCP_TLS).
> +

Can you keep the TLS attributes together?
That way it's easier to figure out which attributes one need to look at
when checking the TLS status.

> +What:		/sys/class/nvme/nvmeX/passthru_err_log_enabled
> +What:		/sys/block/nvmeXnY/passthru_err_log_enabled
> +Date:		January 2024
> +KernelVersion:	6.8
> +Contact:	Alan Adamson <[email protected]>
> +Description:
> +		Shows or sets whether passthrough error logging is enabled.
> +		Reading returns "on" or "off". Writing accepts a boolean
> +		value. The controller-level attribute controls admin
> +		passthrough logging; the namespace-level attribute controls
> +		I/O passthrough logging.
> +
> +What:		/sys/block/nvmeXnY/csi
> +What:		/sys/block/nvmeXnY/metadata_bytes
> +What:		/sys/block/nvmeXnY/nuse
> +Date:		December 2023
> +KernelVersion:	6.8
> +Contact:	Daniel Wagner <[email protected]>
> +Description:
> +		csi: Shows the Command Set Identifier for this namespace.
> +
> +		metadata_bytes: Shows the metadata size in bytes.
> +
> +		nuse: Shows the Namespace Utilization (NUSE) value. Reading
> +		triggers an Identify Namespace command to refresh the
> +		value (rate-limited to avoid excessive commands).
> +
> +What:		/sys/block/nvmeXnY/queue_depth
> +Date:		June 2024
> +KernelVersion:	6.11
> +Contact:	Thomas Song <[email protected]>
> +Description:
> +		Shows the current active I/O count on this path's
> +		controller. Returns empty if iopolicy is not "queue-depth".
> +		Only visible on per-path devices.
> +		Requires CONFIG_NVME_MULTIPATH.
> +
> +What:		/sys/class/nvme/nvmeX/tls_configured_key
> +Date:		July 2024
> +KernelVersion:	6.12
> +Contact:	Hannes Reinecke <[email protected]>
> +Description:
> +		Shows the serial of the configured TLS key. Writing 0
> +		triggers a PSK reauthentication (REPLACETLSPSK) with
> +		the target. After reauthentication the returned serial
> +		will be the new key. Only available for TCP controllers
> +		with secure concatenation enabled (CONFIG_NVME_TCP_TLS).
> +
> +What:		/sys/class/nvme/nvmeX/tls_keyring
> +Date:		July 2024
> +KernelVersion:	6.12
> +Contact:	Hannes Reinecke <[email protected]>
> +Description:
> +		Shows the TLS keyring description. Only available for TCP
> +		controllers with a keyring configured (CONFIG_NVME_TCP_TLS).
> +
> +What:		/sys/block/nvmeXnY/numa_nodes
> +Date:		January 2025
> +KernelVersion:	6.15
> +Contact:	Nilay Shroff <[email protected]>
> +Description:
> +		Shows the NUMA node mask for which this path is the
> +		currently selected path. Returns empty if iopolicy is not
> +		"numa". Only visible on per-path devices.
> +		Requires CONFIG_NVME_MULTIPATH.
> +
> +What:		/sys/block/nvmeXnY/delayed_removal_secs
> +Date:		May 2025
> +KernelVersion:	6.16
> +Contact:	Nilay Shroff <[email protected]>
> +Description:
> +		Shows or sets the delayed removal timeout in seconds for
> +		the multipath head device. When nonzero, I/O is queued
> +		instead of failed when all paths are gone, and head removal
> +		is deferred. Only visible on multipath head devices.
> +		Requires CONFIG_NVME_MULTIPATH.
> +
> +What:		/sys/class/nvme/nvmeX/quirks
>   Date:		November 2025
> -KernelVersion:	6.19
> -Contact:	Linux NVMe mailing list <[email protected]>
> +KernelVersion:	7.0
> +Contact:	Maurizio Lombardi <[email protected]>
>   Description:
> -		The file is avaliable when using a secure concatanation
> -		connection to a NVMe target. Reading the file will return
> -		the serial of the currently negotiated key.
> +		Shows the active quirk names for this controller, one per
> +		line. Shows "none" if no quirks are active.
> +
> +What:		/sys/class/nvme/nvmeX/tls_mode
> +Date:		April 2026
> +KernelVersion:	7.1
> +Contact:	Daniel Wagner <[email protected]>
> +Description:
> +		Shows the TLS mode: "tls" for direct TLS or "concat" for
> +		secure concatenation. Only available for TCP controllers
> +		with TLS or secure concatenation enabled
> +		(CONFIG_NVME_TCP_TLS).
> +
> +What:		/sys/class/nvme/nvmeX/admin_timeout
> +What:		/sys/class/nvme/nvmeX/io_timeout
> +Date:		May 2026
> +KernelVersion:	7.2
> +Contact:	Maurizio Lombardi <[email protected]>
> +Description:
> +		admin_timeout: Shows or sets the admin command timeout in
> +		milliseconds.
> +
> +		io_timeout: Shows or sets the I/O command timeout in
> +		milliseconds. Changes are propagated to all namespace
> +		request queues.
> +
> +		The value must be nonzero. Only writable after the
> +		controller has been started at least once.
> +
> +What:		/sys/class/nvme/nvmeX/diag/command_error_count
> +What:		/sys/class/nvme/nvmeX/diag/reset_count
> +What:		/sys/class/nvme/nvmeX/diag/reconnect_count
> +Date:		May 2026
> +KernelVersion:	7.2
> +Contact:	Nilay Shroff <[email protected]>
> +Description:
> +		Controller diagnostic counters.
> +
> +		command_error_count: Admin command error counter.
> +
> +		reset_count: Controller reset counter.
> +
> +		reconnect_count: Accumulated reconnect counter. Only
> +		available for fabrics controllers.
> +
> +		All counters can be reset by writing a value.
> +
> +What:		/sys/block/nvmeXnY/diag/command_retries_count
> +What:		/sys/block/nvmeXnY/diag/command_error_count
> +What:		/sys/block/nvmeXnY/diag/multipath_failover_count
> +What:		/sys/block/nvmeXnY/diag/io_requeue_no_usable_path_count
> +What:		/sys/block/nvmeXnY/diag/io_fail_no_available_path_count
> +Date:		May 2026
> +KernelVersion:	7.2
> +Contact:	Nilay Shroff <[email protected]>
> +Description:
> +		Namespace diagnostic counters.
> +
> +		command_retries_count: I/O command retry counter. Only
> +		visible on per-path devices.
> +
> +		command_error_count: I/O command error counter. Only
> +		visible on per-path devices.
> +
> +		multipath_failover_count: Multipath failover counter.
> +		Only visible on per-path devices. Requires
> +		CONFIG_NVME_MULTIPATH.
> +
> +		io_requeue_no_usable_path_count: Counter of I/Os requeued
> +		because no usable path was available. Only visible on
> +		multipath head devices. Requires CONFIG_NVME_MULTIPATH.
> +
> +		io_fail_no_available_path_count: Counter of I/Os failed
> +		because no available path existed. Only visible on
> +		multipath head devices. Requires CONFIG_NVME_MULTIPATH.
>   
> -		Writing 0 to the file will trigger a PSK reauthentication
> -		(REPLACETLSPSK) with the target. After a reauthentication
> -		the value returned by tls_configured_key will be the new
> -		serial.
> +		All counters can be reset by writing a value.

Otherwise looks good.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
[email protected]                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich