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authorKlaus Jensen <k.jensen@samsung.com>2021-04-08 11:11:02 +0200
committerKlaus Jensen <k.jensen@samsung.com>2021-04-12 07:05:31 +0200
commita3d9f3a9629bfb22864e83e73f047cd62e9ba283 (patch)
tree7524ad912ba8e95e7698732a9ab26771dbfc3e4a /docs/system
parent555249a59e9cdd6b58da103aba5cf3a2d45c899f (diff)
docs: add nvme emulation documentation
Remove the docs/specs/nvme.txt and replace it with proper documentation in docs/system/nvme.rst. Signed-off-by: Klaus Jensen <k.jensen@samsung.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Diffstat (limited to 'docs/system')
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-rw-r--r--docs/system/nvme.rst225
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diff --git a/docs/system/index.rst b/docs/system/index.rst
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--- a/docs/system/index.rst
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@@ -23,6 +23,7 @@ Contents:
net
virtio-net-failover
usb
+ nvme
ivshmem
linuxboot
generic-loader
diff --git a/docs/system/nvme.rst b/docs/system/nvme.rst
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--- /dev/null
+++ b/docs/system/nvme.rst
@@ -0,0 +1,225 @@
+==============
+NVMe Emulation
+==============
+
+QEMU provides NVMe emulation through the ``nvme``, ``nvme-ns`` and
+``nvme-subsys`` devices.
+
+See the following sections for specific information on
+
+ * `Adding NVMe Devices`_, `additional namespaces`_ and `NVM subsystems`_.
+ * Configuration of `Optional Features`_ such as `Controller Memory Buffer`_,
+ `Simple Copy`_, `Zoned Namespaces`_, `metadata`_ and `End-to-End Data
+ Protection`_,
+
+Adding NVMe Devices
+===================
+
+Controller Emulation
+--------------------
+
+The QEMU emulated NVMe controller implements version 1.4 of the NVM Express
+specification. All mandatory features are implement with a couple of exceptions
+and limitations:
+
+ * Accounting numbers in the SMART/Health log page are reset when the device
+ is power cycled.
+ * Interrupt Coalescing is not supported and is disabled by default.
+
+The simplest way to attach an NVMe controller on the QEMU PCI bus is to add the
+following parameters:
+
+.. code-block:: console
+
+ -drive file=nvm.img,if=none,id=nvm
+ -device nvme,serial=deadbeef,drive=nvm
+
+There are a number of optional general parameters for the ``nvme`` device. Some
+are mentioned here, but see ``-device nvme,help`` to list all possible
+parameters.
+
+``max_ioqpairs=UINT32`` (default: ``64``)
+ Set the maximum number of allowed I/O queue pairs. This replaces the
+ deprecated ``num_queues`` parameter.
+
+``msix_qsize=UINT16`` (default: ``65``)
+ The number of MSI-X vectors that the device should support.
+
+``mdts=UINT8`` (default: ``7``)
+ Set the Maximum Data Transfer Size of the device.
+
+``use-intel-id`` (default: ``off``)
+ Since QEMU 5.2, the device uses a QEMU allocated "Red Hat" PCI Device and
+ Vendor ID. Set this to ``on`` to revert to the unallocated Intel ID
+ previously used.
+
+Additional Namespaces
+---------------------
+
+In the simplest possible invocation sketched above, the device only support a
+single namespace with the namespace identifier ``1``. To support multiple
+namespaces and additional features, the ``nvme-ns`` device must be used.
+
+.. code-block:: console
+
+ -device nvme,id=nvme-ctrl-0,serial=deadbeef
+ -drive file=nvm-1.img,if=none,id=nvm-1
+ -device nvme-ns,drive=nvm-1
+ -drive file=nvm-2.img,if=none,id=nvm-2
+ -device nvme-ns,drive=nvm-2
+
+The namespaces defined by the ``nvme-ns`` device will attach to the most
+recently defined ``nvme-bus`` that is created by the ``nvme`` device. Namespace
+identifers are allocated automatically, starting from ``1``.
+
+There are a number of parameters available:
+
+``nsid`` (default: ``0``)
+ Explicitly set the namespace identifier.
+
+``uuid`` (default: *autogenerated*)
+ Set the UUID of the namespace. This will be reported as a "Namespace UUID"
+ descriptor in the Namespace Identification Descriptor List.
+
+``bus``
+ If there are more ``nvme`` devices defined, this parameter may be used to
+ attach the namespace to a specific ``nvme`` device (identified by an ``id``
+ parameter on the controller device).
+
+NVM Subsystems
+--------------
+
+Additional features becomes available if the controller device (``nvme``) is
+linked to an NVM Subsystem device (``nvme-subsys``).
+
+The NVM Subsystem emulation allows features such as shared namespaces and
+multipath I/O.
+
+.. code-block:: console
+
+ -device nvme-subsys,id=nvme-subsys-0,nqn=subsys0
+ -device nvme,serial=a,subsys=nvme-subsys-0
+ -device nvme,serial=b,subsys=nvme-subsys-0
+
+This will create an NVM subsystem with two controllers. Having controllers
+linked to an ``nvme-subsys`` device allows additional ``nvme-ns`` parameters:
+
+``shared`` (default: ``off``)
+ Specifies that the namespace will be attached to all controllers in the
+ subsystem. If set to ``off`` (the default), the namespace will remain a
+ private namespace and may only be attached to a single controller at a time.
+
+``detached`` (default: ``off``)
+ If set to ``on``, the namespace will be be available in the subsystem, but
+ not attached to any controllers initially.
+
+Thus, adding
+
+.. code-block:: console
+
+ -drive file=nvm-1.img,if=none,id=nvm-1
+ -device nvme-ns,drive=nvm-1,nsid=1,shared=on
+ -drive file=nvm-2.img,if=none,id=nvm-2
+ -device nvme-ns,drive=nvm-2,nsid=3,detached=on
+
+will cause NSID 1 will be a shared namespace (due to ``shared=on``) that is
+initially attached to both controllers. NSID 3 will be a private namespace
+(i.e. only attachable to a single controller at a time) and will not be
+attached to any controller initially (due to ``detached=on``).
+
+Optional Features
+=================
+
+Controller Memory Buffer
+------------------------
+
+``nvme`` device parameters related to the Controller Memory Buffer support:
+
+``cmb_size_mb=UINT32`` (default: ``0``)
+ This adds a Controller Memory Buffer of the given size at offset zero in BAR
+ 2.
+
+``legacy-cmb`` (default: ``off``)
+ By default, the device uses the "v1.4 scheme" for the Controller Memory
+ Buffer support (i.e, the CMB is initially disabled and must be explicitly
+ enabled by the host). Set this to ``on`` to behave as a v1.3 device wrt. the
+ CMB.
+
+Simple Copy
+-----------
+
+The device includes support for TP 4065 ("Simple Copy Command"). A number of
+additional ``nvme-ns`` device parameters may be used to control the Copy
+command limits:
+
+``mssrl=UINT16`` (default: ``128``)
+ Set the Maximum Single Source Range Length (``MSSRL``). This is the maximum
+ number of logical blocks that may be specified in each source range.
+
+``mcl=UINT32`` (default: ``128``)
+ Set the Maximum Copy Length (``MCL``). This is the maximum number of logical
+ blocks that may be specified in a Copy command (the total for all source
+ ranges).
+
+``msrc=UINT8`` (default: ``127``)
+ Set the Maximum Source Range Count (``MSRC``). This is the maximum number of
+ source ranges that may be used in a Copy command. This is a 0's based value.
+
+Zoned Namespaces
+----------------
+
+A namespaces may be "Zoned" as defined by TP 4053 ("Zoned Namespaces"). Set
+``zoned=on`` on an ``nvme-ns`` device to configure it as a zoned namespace.
+
+The namespace may be configured with additional parameters
+
+``zoned.zone_size=SIZE`` (default: ``128MiB``)
+ Define the zone size (``ZSZE``).
+
+``zoned.zone_capacity=SIZE`` (default: ``0``)
+ Define the zone capacity (``ZCAP``). If left at the default (``0``), the zone
+ capacity will equal the zone size.
+
+``zoned.descr_ext_size=UINT32`` (default: ``0``)
+ Set the Zone Descriptor Extension Size (``ZDES``). Must be a multiple of 64
+ bytes.
+
+``zoned.cross_read=BOOL`` (default: ``off``)
+ Set to ``on`` to allow reads to cross zone boundaries.
+
+``zoned.max_active=UINT32`` (default: ``0``)
+ Set the maximum number of active resources (``MAR``). The default (``0``)
+ allows all zones to be active.
+
+``zoned.max_open=UINT32`` (default: ``0``)
+ Set the maximum number of open resources (``MOR``). The default (``0``)
+ allows all zones to be open. If ``zoned.max_active`` is specified, this value
+ must be less than or equal to that.
+
+Metadata
+--------
+
+The virtual namespace device supports LBA metadata in the form separate
+metadata (``MPTR``-based) and extended LBAs.
+
+``ms=UINT16`` (default: ``0``)
+ Defines the number of metadata bytes per LBA.
+
+``mset=UINT8`` (default: ``0``)
+ Set to ``1`` to enable extended LBAs.
+
+End-to-End Data Protection
+--------------------------
+
+The virtual namespace device supports DIF- and DIX-based protection information
+(depending on ``mset``).
+
+``pi=UINT8`` (default: ``0``)
+ Enable protection information of the specified type (type ``1``, ``2`` or
+ ``3``).
+
+``pil=UINT8`` (default: ``0``)
+ Controls the location of the protection information within the metadata. Set
+ to ``1`` to transfer protection information as the first eight bytes of
+ metadata. Otherwise, the protection information is transferred as the last
+ eight bytes.