238 lines
8.2 KiB
ReStructuredText
238 lines
8.2 KiB
ReStructuredText
==============
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NVMe Emulation
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==============
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QEMU provides NVMe emulation through the ``nvme``, ``nvme-ns`` and
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``nvme-subsys`` devices.
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See the following sections for specific information on
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* `Adding NVMe Devices`_, `additional namespaces`_ and `NVM subsystems`_.
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* Configuration of `Optional Features`_ such as `Controller Memory Buffer`_,
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`Simple Copy`_, `Zoned Namespaces`_, `metadata`_ and `End-to-End Data
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Protection`_,
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Adding NVMe Devices
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===================
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Controller Emulation
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--------------------
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The QEMU emulated NVMe controller implements version 1.4 of the NVM Express
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specification. All mandatory features are implement with a couple of exceptions
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and limitations:
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* Accounting numbers in the SMART/Health log page are reset when the device
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is power cycled.
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* Interrupt Coalescing is not supported and is disabled by default.
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The simplest way to attach an NVMe controller on the QEMU PCI bus is to add the
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following parameters:
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.. code-block:: console
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-drive file=nvm.img,if=none,id=nvm
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-device nvme,serial=deadbeef,drive=nvm
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There are a number of optional general parameters for the ``nvme`` device. Some
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are mentioned here, but see ``-device nvme,help`` to list all possible
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parameters.
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``max_ioqpairs=UINT32`` (default: ``64``)
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Set the maximum number of allowed I/O queue pairs. This replaces the
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deprecated ``num_queues`` parameter.
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``msix_qsize=UINT16`` (default: ``65``)
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The number of MSI-X vectors that the device should support.
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``mdts=UINT8`` (default: ``7``)
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Set the Maximum Data Transfer Size of the device.
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``use-intel-id`` (default: ``off``)
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Since QEMU 5.2, the device uses a QEMU allocated "Red Hat" PCI Device and
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Vendor ID. Set this to ``on`` to revert to the unallocated Intel ID
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previously used.
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Additional Namespaces
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---------------------
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In the simplest possible invocation sketched above, the device only support a
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single namespace with the namespace identifier ``1``. To support multiple
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namespaces and additional features, the ``nvme-ns`` device must be used.
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.. code-block:: console
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-device nvme,id=nvme-ctrl-0,serial=deadbeef
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-drive file=nvm-1.img,if=none,id=nvm-1
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-device nvme-ns,drive=nvm-1
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-drive file=nvm-2.img,if=none,id=nvm-2
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-device nvme-ns,drive=nvm-2
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The namespaces defined by the ``nvme-ns`` device will attach to the most
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recently defined ``nvme-bus`` that is created by the ``nvme`` device. Namespace
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identifers are allocated automatically, starting from ``1``.
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There are a number of parameters available:
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``nsid`` (default: ``0``)
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Explicitly set the namespace identifier.
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``uuid`` (default: *autogenerated*)
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Set the UUID of the namespace. This will be reported as a "Namespace UUID"
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descriptor in the Namespace Identification Descriptor List.
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``eui64``
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Set the EUI-64 of the namespace. This will be reported as a "IEEE Extended
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Unique Identifier" descriptor in the Namespace Identification Descriptor List.
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Since machine type 6.1 a non-zero default value is used if the parameter
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is not provided. For earlier machine types the field defaults to 0.
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``bus``
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If there are more ``nvme`` devices defined, this parameter may be used to
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attach the namespace to a specific ``nvme`` device (identified by an ``id``
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parameter on the controller device).
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NVM Subsystems
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--------------
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Additional features becomes available if the controller device (``nvme``) is
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linked to an NVM Subsystem device (``nvme-subsys``).
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The NVM Subsystem emulation allows features such as shared namespaces and
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multipath I/O.
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.. code-block:: console
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-device nvme-subsys,id=nvme-subsys-0,nqn=subsys0
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-device nvme,serial=a,subsys=nvme-subsys-0
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-device nvme,serial=b,subsys=nvme-subsys-0
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This will create an NVM subsystem with two controllers. Having controllers
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linked to an ``nvme-subsys`` device allows additional ``nvme-ns`` parameters:
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``shared`` (default: ``off``)
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Specifies that the namespace will be attached to all controllers in the
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subsystem. If set to ``off`` (the default), the namespace will remain a
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private namespace and may only be attached to a single controller at a time.
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``detached`` (default: ``off``)
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If set to ``on``, the namespace will be be available in the subsystem, but
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not attached to any controllers initially.
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Thus, adding
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.. code-block:: console
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-drive file=nvm-1.img,if=none,id=nvm-1
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-device nvme-ns,drive=nvm-1,nsid=1,shared=on
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-drive file=nvm-2.img,if=none,id=nvm-2
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-device nvme-ns,drive=nvm-2,nsid=3,detached=on
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will cause NSID 1 will be a shared namespace (due to ``shared=on``) that is
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initially attached to both controllers. NSID 3 will be a private namespace
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(i.e. only attachable to a single controller at a time) and will not be
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attached to any controller initially (due to ``detached=on``).
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Optional Features
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=================
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Controller Memory Buffer
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------------------------
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``nvme`` device parameters related to the Controller Memory Buffer support:
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``cmb_size_mb=UINT32`` (default: ``0``)
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This adds a Controller Memory Buffer of the given size at offset zero in BAR
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2.
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``legacy-cmb`` (default: ``off``)
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By default, the device uses the "v1.4 scheme" for the Controller Memory
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Buffer support (i.e, the CMB is initially disabled and must be explicitly
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enabled by the host). Set this to ``on`` to behave as a v1.3 device wrt. the
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CMB.
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Simple Copy
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-----------
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The device includes support for TP 4065 ("Simple Copy Command"). A number of
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additional ``nvme-ns`` device parameters may be used to control the Copy
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command limits:
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``mssrl=UINT16`` (default: ``128``)
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Set the Maximum Single Source Range Length (``MSSRL``). This is the maximum
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number of logical blocks that may be specified in each source range.
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``mcl=UINT32`` (default: ``128``)
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Set the Maximum Copy Length (``MCL``). This is the maximum number of logical
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blocks that may be specified in a Copy command (the total for all source
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ranges).
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``msrc=UINT8`` (default: ``127``)
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Set the Maximum Source Range Count (``MSRC``). This is the maximum number of
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source ranges that may be used in a Copy command. This is a 0's based value.
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Zoned Namespaces
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----------------
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A namespaces may be "Zoned" as defined by TP 4053 ("Zoned Namespaces"). Set
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``zoned=on`` on an ``nvme-ns`` device to configure it as a zoned namespace.
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The namespace may be configured with additional parameters
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``zoned.zone_size=SIZE`` (default: ``128MiB``)
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Define the zone size (``ZSZE``).
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``zoned.zone_capacity=SIZE`` (default: ``0``)
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Define the zone capacity (``ZCAP``). If left at the default (``0``), the zone
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capacity will equal the zone size.
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``zoned.descr_ext_size=UINT32`` (default: ``0``)
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Set the Zone Descriptor Extension Size (``ZDES``). Must be a multiple of 64
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bytes.
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``zoned.cross_read=BOOL`` (default: ``off``)
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Set to ``on`` to allow reads to cross zone boundaries.
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``zoned.max_active=UINT32`` (default: ``0``)
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Set the maximum number of active resources (``MAR``). The default (``0``)
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allows all zones to be active.
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``zoned.max_open=UINT32`` (default: ``0``)
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Set the maximum number of open resources (``MOR``). The default (``0``)
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allows all zones to be open. If ``zoned.max_active`` is specified, this value
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must be less than or equal to that.
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``zoned.zasl=UINT8`` (default: ``0``)
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Set the maximum data transfer size for the Zone Append command. Like
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``mdts``, the value is specified as a power of two (2^n) and is in units of
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the minimum memory page size (CAP.MPSMIN). The default value (``0``)
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has this property inherit the ``mdts`` value.
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Metadata
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--------
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The virtual namespace device supports LBA metadata in the form separate
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metadata (``MPTR``-based) and extended LBAs.
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``ms=UINT16`` (default: ``0``)
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Defines the number of metadata bytes per LBA.
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``mset=UINT8`` (default: ``0``)
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Set to ``1`` to enable extended LBAs.
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End-to-End Data Protection
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--------------------------
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The virtual namespace device supports DIF- and DIX-based protection information
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(depending on ``mset``).
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``pi=UINT8`` (default: ``0``)
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Enable protection information of the specified type (type ``1``, ``2`` or
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``3``).
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``pil=UINT8`` (default: ``0``)
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Controls the location of the protection information within the metadata. Set
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to ``1`` to transfer protection information as the first eight bytes of
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metadata. Otherwise, the protection information is transferred as the last
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eight bytes.
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