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

[zhenwei pi <pizhenwei@bytedance.com>]

On 5/31/23 22:06, Stefan Hajnoczi wrote:
> 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?

Sorry, I missed the address and port. They should be:
virtio-rdma://192.168.1.100:8549/blk-resource/nvme-pool/849a39ad-8d7b-4a7a-adb6-e7407ace532c
virtio-tcp://192.168.1.110/blk-resource/hdd-pool/238151a7-acd7-4621-bbdf-382ddbccb6a1
...

This is human readable string. when the software(or hardware) handles 
this, this should be translated into:
transport: RDMA
address: 192.168.1.100
port: 8549 (default port 8549(CRC-16/ARC of "Virtio"))
target VQN: blk-resource/hdd-pool/238151a7-acd7-4621-bbdf-382ddbccb6a1

This section only defines the "VQN" schema, not the resource string schema.

For a process, I think the following two are both fine:
./foo --full-url 
virtio-rdma://192.168.1.100:8549/blk-resource/nvme-pool/849a39ad-8d7b-4a7a-adb6-e7407ace532c
./foo --transport rdma --address 192.168.1.100 --port 8549 --tvqn
blk-resource/hdd-pool/238151a7-acd7-4621-bbdf-382ddbccb6a1

[snip]

> 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.
OK, fix this in the next version.

> > +\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

--
zhenwei pi