Re: [PATCH v4 1/2] dt-bindings: microsoft: Add vmbus message-connection-id property

[Krzysztof Kozlowski <krzk@kernel.org>]

On 05/11/2025 02:10, Hardik Garg wrote:
> 
> Each guest has a private hypervisor mailbox and cannot access any other
> guest’s communication path. Using an incorrect connection ID does not
> allow eavesdropping or cause interference — it only results in failed
> VMBus initialization because the host drops messages sent to an
> unexpected port. Thus, exposing the correct connection ID to the guest
> is safe and necessary for correct initialization.
> 
>> If different values are important for the host, then all guests should
>> use whatever 0 which will map to different values on host by other means
>> of your protocol.
>>
> 
> Using a fixed value such as 0 for all guests would not work, because the
> Hyper-V host differentiates between multiple control-plane contexts (for
> example, VTL0 vs VTL2) using distinct connection IDs. The guest must use
> the value assigned by the host, as there is no implicit mapping or
> negotiation protocol to determine it otherwise.

Sorry, I am not going back to three months old discussion.

Therefore I close this topic for me with: since the actual value does
not matter for the host - it will discard all messages which are not
intended to this guest - you can just use value 0 and your hypervisor
will map to proper port.

Best regards,
Krzysztof