[PATCH RFC v2 16/16] docs: add documentation for experimental nvme emulation

[Klaus Jensen <its@irrelevant.dk>]

From: Klaus Jensen <k.jensen@samsung.com>

Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
---
 docs/system/device-emulation.rst          |   1 +
 docs/system/devices/nvme-experimental.rst | 107 ++++++++++++++++++++++
 2 files changed, 108 insertions(+)
 create mode 100644 docs/system/devices/nvme-experimental.rst

diff --git a/docs/system/device-emulation.rst b/docs/system/device-emulation.rst
index 7afcfd8064ae..9a4e08e4ea44 100644
--- a/docs/system/device-emulation.rst
+++ b/docs/system/device-emulation.rst
@@ -85,6 +85,7 @@ Emulated Devices
    devices/ivshmem.rst
    devices/net.rst
    devices/nvme.rst
+   devices/nvme-experimental.rst
    devices/usb.rst
    devices/vhost-user.rst
    devices/virtio-pmem.rst
diff --git a/docs/system/devices/nvme-experimental.rst b/docs/system/devices/nvme-experimental.rst
new file mode 100644
index 000000000000..d3b94dc3ef59
--- /dev/null
+++ b/docs/system/devices/nvme-experimental.rst
@@ -0,0 +1,107 @@
+===========================
+Experimental NVMe Emulation
+===========================
+
+QEMU offers experimental NVMe emulation through the ``x-nvme-ctrl`` device and
+the ``x-nvme-subsystem`` and ``x-nvme-ns-{nvm,zoned}`` objects.
+
+
+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
+
+    -object x-nvme-subsystem,id=nvme-subsys-0
+    -device x-nvme-ctrl,subsys=nvme-subsys-0
+
+There are a number of optional general parameters for the ``x-nvme-ctrl``
+device. Some are mentioned here, but see ``-device x-nvme-ctrl,help`` to list
+all possible parameters.
+
+``max-ioqpairs=UINT32`` (default: ``64``)
+  Set the maximum number of allowed I/O queue pairs.
+
+``msix-vectors=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.
+
+
+Additional Namespaces
+---------------------
+
+The invocation sketched above does not add any namespaces to the subsystem. To
+add these, add ``x-nvme-ns-NSTYPE`` (where ``NSTYPE`` is either ``nvm`` or
+``zoned``) objects with attached blockdevs and a reference to the subsystem:
+
+.. code-block:: console
+
+    -blockdev file,node-name=blk-file-nvm-1,filename=nvm-1.img
+    -blockdev raw,node-name=blk-nvm-1,file=blk-file-nvm-1
+    -object x-nvme-ns-nvm,id=nvm-1,blockdev=blk-nvm-1,subsys=nvme-subsys-0
+
+There are a number of optional parameters available (common to both the ``nvm``
+and ``zoned`` namespace types):
+
+``nsid`` (default: ``"auto"``)
+  Explicitly set the namespace identifier. If left at the default, the
+  subsystem will allocate the next available identifier.
+
+``uuid`` (default: ``"auto"``)
+  Set the UUID of the namespace. This will be reported as a "Namespace UUID"
+  descriptor in the Namespace Identification Descriptor List. If left at the
+  default, a UUID will be generated.
+
+``eui64`` (default: ``"auto"``)
+  Set the EUI-64 of the namespace. This will be reported as a "IEEE Extended
+  Unique Identifier" descriptor in the Namespace Identification Descriptor
+  List. If left at the default, an identifier prefixed with the QEMU IEEE OUI
+  (``52:54:00``) will be generated.
+
+``lba-size`` (default: ``4096``)
+  Set the logical block size.
+
+Namespaces support LBA metadata in the form separate metadata (``MPTR``-based)
+and extended LBAs.
+
+``metadata-size`` (default: ``0``)
+  Defines the number of metadata bytes per LBA.
+
+``extended-lba`` (default: ``off/false``)
+  Set to ``on/true`` to enable extended LBAs.
+
+With metadata configured, namespaces support DIF- and DIX-based protection
+information (depending on ``extended-lba``).
+
+``pi-type`` (default: ``"none"``)
+  Enable protection information of the specified type (type ``"type1"``,
+  ``"type2"`` or ``"type3"``).
+
+``pi-first`` (default: ``off/false``)
+  Controls the location of the protection information within the metadata. Set
+  to ``on/true`` to transfer protection information as the first eight bytes of
+  metadata. Otherwise, the protection information is transferred as the last
+  eight bytes.
+
+The ``zoned`` namespace type has additional parameters:
+
+``zone-size`` (default: ``4096``)
+  The number of LBAs in a zone.
+
+``zone-capacity`` (default: ``4096``)
+  The number of writable LBAs in a zone.
-- 
2.33.0