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

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Sun, Jun 04, 2023 at 10:40:06PM -0400, Parav Pandit wrote:
> 
> 
> On 6/1/2023 9:50 PM, zhenwei pi wrote:
> > 
> > 
> > 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
> 
> Since it is device specific resource, may be blk-dev or blk-device reads
> better, as behind this device there are multiple resources.
> 
> > ...
> > 
> > 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.
> s/NUL/NULL ?

I like to use the ASCII "NUL" character name because that avoids
confusion with other concepts of nullness in programming:

  "It is often abbreviated as NUL (or NULL, though in some contexts that
  term is used for the null pointer)"

https://en.wikipedia.org/wiki/NUL_character

Stefan

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