[PATCH v7 4/4] docs: Add generic vhost-vdpa device documentation

[Longpeng(Mike)]

From: Longpeng <longpeng2@huawei.com>

Signed-off-by: Longpeng <longpeng2@huawei.com>
---
 docs/system/devices/vhost-vdpa-device.rst | 43 +++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 docs/system/devices/vhost-vdpa-device.rst

diff --git a/docs/system/devices/vhost-vdpa-device.rst 
b/docs/system/devices/vhost-vdpa-device.rst
new file mode 100644
index 0000000000..50173299e0
--- /dev/null
+++ b/docs/system/devices/vhost-vdpa-device.rst
@@ -0,0 +1,43 @@
+
+=========================
+generic vhost-vdpa device
+=========================
+
+This document explains the usage of the generic vhost vdpa device.
+
+Description
+-----------
+
+vDPA(virtio data path acceleration) device is a device that uses a datapath
+which complies with the virtio specifications with vendor specific control
+path.
+
+QEMU provides two types of vhost-vdpa devices to enable the vDPA device, one
+is type sensitive which means QEMU needs to know the actual device type
+(e.g. net, blk, scsi) and another is called "generic vdpa device" which is
+type insensitive (likes vfio-pci). 
+
+Examples
+--------
+
+Prepare the vhost-vdpa backends first:
+
+::
+  host# ls -l /dev/vhost-vdpa-*
+  crw------- 1 root root 236, 0 Nov  2 00:49 /dev/vhost-vdpa-0
+
+Start QEMU with virtio-mmio bus:
+
+::
+  host# qemu-system                                                  \
+      -M microvm -m 512 -smp 2 -kernel ... -initrd ...               \
+      -device vhost-vdpa-device,vhostdev=/dev/vhost-vdpa-0           \
+      ...
+
+Start QEMU with virtio-pci bus:
+
+::
+  host# qemu-system                                                  \
+      -M pc -m 512 -smp 2                                            \
+      -device vhost-vdpa-device-pci,vhostdev=/dev/vhost-vdpa-0       \
+      ...
-- 
2.23.0