linux-kernel - Re: [PATCH] Documentation: add basic information on vDPA

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Date:   Thu, 18 Aug 2022 16:05:08 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Stefan Hajnoczi <stefanha@...hat.com>
Cc:     virtualization <virtualization@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Stefano Garzarella <sgarzare@...hat.com>
Subject: Re: [PATCH] Documentation: add basic information on vDPA

On Thu, Aug 18, 2022 at 6:20 AM Stefan Hajnoczi <stefanha@...hat.com> wrote:
>
> The vDPA driver framework is largely undocumented. Add a basic page that
> describes what vDPA is, where to get more information, and how to use
> the simulator for testing.
>
> In the future it would be nice to add an overview of the driver API as
> well as comprehensive doc comments.

+1

>
> Cc: "Michael S. Tsirkin" <mst@...hat.com>
> Cc: Jason Wang <jasowang@...hat.com>
> Cc: Stefano Garzarella <sgarzare@...hat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@...hat.com>

Acked-by: Jason Wang <jasowang@...hat.com>

> ---
>  Documentation/driver-api/index.rst |  1 +
>  Documentation/driver-api/vdpa.rst  | 40 ++++++++++++++++++++++++++++++
>  2 files changed, 41 insertions(+)
>  create mode 100644 Documentation/driver-api/vdpa.rst
>
> diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst
> index d3a58f77328e..e307779568d4 100644
> --- a/Documentation/driver-api/index.rst
> +++ b/Documentation/driver-api/index.rst
> @@ -103,6 +103,7 @@ available subsections can be seen below.
>     switchtec
>     sync_file
>     tty/index
> +   vdpa
>     vfio-mediated-device
>     vfio
>     vfio-pci-device-specific-driver-acceptance
> diff --git a/Documentation/driver-api/vdpa.rst b/Documentation/driver-api/vdpa.rst
> new file mode 100644
> index 000000000000..75c666548e1d
> --- /dev/null
> +++ b/Documentation/driver-api/vdpa.rst
> @@ -0,0 +1,40 @@
> +====================================
> +vDPA - VIRTIO Data Path Acceleration
> +====================================
> +
> +The vDPA driver framework can be used to implement VIRTIO devices that are
> +backed by physical hardware or by software. While the device's data path
> +complies with the VIRTIO specification, the control path is driver-specific and
> +a netlink interface exists for instantiating devices.
> +
> +vDPA devices can be attached to the kernel's VIRTIO device drivers or exposed
> +to userspace emulators/virtualizers such as QEMU through vhost.
> +
> +The driver API is not documented beyond the doc comments in <linux/vdpa.h>. The
> +netlink API is not documented beyond the doc comments in <linux/uapi/vdpa.h>.
> +The existing vDPA drivers serve as reference code for those wishing to develop
> +their own drivers.
> +
> +See https://vdpa-dev.gitlab.io/ for more information about vDPA.
> +
> +Questions can be sent to the virtualization@...ts.linux-foundation.org mailing
> +list.
> +
> +Device simulators
> +-----------------
> +
> +There are software vDPA device simulators for testing, prototyping, and
> +development purposes. The simulators do not require physical hardware.
> +
> +Available simulators include:
> +
> +- `vdpa_sim_net` implements a virtio-net loopback device.
> +- `vdpa_sim_blk` implements a memory-backed virtio-blk device.
> +
> +To use `vdpa_sim_blk` through vhost::
> +
> +  # modprobe vhost_vdpa
> +  # modprobe vdpa_sim_blk
> +  # vdpa dev add name vdpa-blk1 mgmtdev vdpasim_blk
> +  ...use /dev/vhost-dev-0...
> +  # vdpa dev del vdpa-blk1
> --
> 2.37.2
>