Re: [virtio-comment] [PATCH v2 01/11] transport-fabrics: introduce Virtio Over Fabrics overview

[Parav Pandit <parav@nvidia.com>]

On 5/4/2023 4:19 AM, zhenwei pi wrote:
> In the past years, virtio supports lots of device specifications by

> PCI/MMIO/CCW. These devices work fine in the virtualization environment.
>
> Introduce Virtio Over Fabrics transport to support "network defined
s/network defined/network attached

> peripheral devices". With this transport, Many Virtio based devices
> transparently work over fabrics. 
I am not sure transparently.
Probably just better to say works over fabrics.

> Note that the balloon device may not
> make sense. Shared memory regions won't work.

> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
> ---
>   content.tex           |  1 +
>   transport-fabrics.tex | 31 +++++++++++++++++++++++++++++++
>   2 files changed, 32 insertions(+)
>   create mode 100644 transport-fabrics.tex
>
> diff --git a/content.tex b/content.tex
> index cff548a..f899c3a 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -582,6 +582,7 @@ \chapter{Virtio Transport Options}\label{sec:Virtio Transport Options}
>   \input{transport-pci.tex}
>   \input{transport-mmio.tex}
>   \input{transport-ccw.tex}
> +\input{transport-fabrics.tex}
>   
>   \chapter{Device Types}\label{sec:Device Types}
>   
> diff --git a/transport-fabrics.tex b/transport-fabrics.tex
> new file mode 100644
> index 0000000..0dc031b
> --- /dev/null
> +++ b/transport-fabrics.tex
> @@ -0,0 +1,31 @@
> +\section{Virtio Over Fabrics}\label{sec:Virtio Transport Options / Virtio Over Fabrics}
> +
> +This section defines specification to Virtio that enables operation over other
> +interconnects. A central goal of Virtio Over Fabrics is to maintain consistency
We have 3 different terminology.
network based
fabrics
and here interconnects

best to drop and stick to fabrics.

> +with the PCI device, so Virtio based devices transparently work over PCI or
> +fabrics.
> +
> +Virtio Over Fabrics uses reliable connection to transmit data, the reliable
> +connection betweens two rules:
> +
s/betweens/between

"betweens two rules" is not reading right.

Virtio over fabrics uses underlying reliable transport to exchange data 
(as it is received also reliably).

because it may be multiple connections.


> +\begin{itemize}
> +\item An initiator functions as an Virtio Over Fabrics client. An initiator
> +typically serves the same purpose to a machine as a Virtio device, issues
> +commands to remote side.
> +\item A target functions as an Virtio Over Fabrics server. An target typically
> +handles commands from the initiator side and responses completions.
> +\end{itemize}
> +
> +Virtio Over Fabrics has the following differences from the PCI based
> +specification:
> +
> +\begin{itemize}
> +\item Instead of memory sharing mechanism of virtqueue, there is a one-to-one
> +mapping between virtqueue and the reliable connection which executes the vring
> +data transmission.
vring is not a well defined spec term today. It is mostly refers to 
legacy part of the spec.
So need to reword this.

> +\item An additional control connection is required to execute control commands
> +which is similar to read/write register on a PCI device.
> +\item Virtio Over Fabrics does not define an interrupt mechanism that allows an
> +initiator to generate a host interrupt. It is the responsibility of the host
> +fabric interface to generate host interrupts.
Please change to notifications as we try to keep the layer as much as 
possible between interrupt and notifications.

> +\end{itemize}