Re: [virtio-comment] [PATCH v2 02/11] transport-fabrics: introduce Virtio Qualified Name

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Thu, May 04, 2023 at 04:19:01PM +0800, zhenwei pi wrote:
> Add VQN section. The VQN is a little different from iSCSI/NVMe-oF on
> style limitation. Because iSCSI/NVMe-of is storage specific protocol,
> the full string IQN(for iSCSI/iSER) and NQN(for NVMe-oF) represents
> a "storage access address". However, Virtio Over Fabrics works as
> transport layer rather than device layer, a URL style string is better
> to Virtio Over Fabrics. For example:
> virtio-of://blk-resource/nvme-pool/849a39ad-8d7b-4a7a-adb6-e7407ace532c
> virtio-of://blk-resource/hdd-pool/238151a7-acd7-4621-bbdf-382ddbccb6a1
> ...
> virtio-of://crypto-resource/25307f22-e5a8-4ea2-b7ca-79f5c3bebc3c

I'm not sure what blk-resource and nvme-pool are in these URLs?

Should the patch mention the virtio-of:// URI scheme?

> 
> A hunam readable VQN is helpful to maintain/debug/distinguish.
> 
> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
> ---
>  transport-fabrics.tex | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/transport-fabrics.tex b/transport-fabrics.tex
> index 0dc031b..26b0192 100644
> --- a/transport-fabrics.tex
> +++ b/transport-fabrics.tex
> @@ -29,3 +29,19 @@ \section{Virtio Over Fabrics}\label{sec:Virtio Transport Options / Virtio Over F
>  initiator to generate a host interrupt. It is the responsibility of the host
>  fabric interface to generate host interrupts.
>  \end{itemize}
> +
> +\subsection{Virtio Qualified Name}\label{sec:Virtio Transport Options / Virtio Over Fabrics / Virtio Qualified Name}
> +Virtio Qualified Names (VQNs) are used to uniquely describe an initiator or a
> +target for the purposes of identification.
> +
> +A VQN is encoded as a string of Unicode characters with the following
> +properties:
> +
> +\begin{itemize}
> +\item The encoding is UTF-8 (refer to RFC 3629).
> +\item The characters dash('-'), dot ('.'), slash('/') and colon(':') are used
> +in formatting.
> +\item The maximum name is 256 bytes in length.
> +\item The string is null terminated.

Is the maximum name 255 UTF-8 bytes plus a NUL character? Please state
this in the spec. For example:

  \item The string is NUL terminated.
  \item The maximum name is 256 bytes in length, including the NUL character.

> +\item There is no strict style limitation.

I think it's necessary to define representations for specific fabrics
(e.g. TCP/IP) so that VQNs can be exchanged between different VIRTIO
implementations (VMMs, DPUs, command-line utilities, etc). Otherwise two
different implementations may represent the same address differently.

Stefan

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