Re: [PATCH v8 5/5] docs: Add generic vhost-vdpa device documentation

[Jason Wang]

On Tue, Nov 8, 2022 at 8:42 AM Longpeng(Mike) <longpeng2@huawei.com> wrote:
>
> 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..b758c4fce6
> --- /dev/null
> +++ b/docs/system/devices/vhost-vdpa-device.rst

If the doc is for a general vhost-vDPA device, we'd better have a better name?

> @@ -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).

Same as above, if this document is focused on the general vhost-vDPA
device, we'd better emphasize it. And I don't think mention vfio-pci
is good idea here since those two are different from a lot of places,
(e.g the general vhost-vdpa is not transport specific, as demonstrated
below).

Thanks

> +
> +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
>