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

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Message-Id: <1753395133-26061-1-git-send-email-hargar@linux.microsoft.com>
Date: Thu, 24 Jul 2025 15:12:13 -0700
From: Hardik Garg <hargar@...ux.microsoft.com>
To: krzk@...nel.org
Cc: apais@...rosoft.com,
	cho@...rosoft.com,
	conor+dt@...nel.org,
	decui@...rosoft.com,
	devicetree@...r.kernel.org,
	haiyangz@...rosoft.com,
	hargar@...ux.microsoft.com,
	hargar@...rosoft.com,
	krzk+dt@...nel.org,
	kys@...rosoft.com,
	linux-hyperv@...r.kernel.org,
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	wei.liu@...nel.org
Subject: Re: [PATCH v4 1/2] dt-bindings: microsoft: Add vmbus message-connection-id property

> Then all guests can use the same value, 0, making this property redundant.

No, they cannot use the same value. The protocol requires different connection IDs for different communication paths.
For example, a guest communicating with a VTL0 control plane uses a different connection ID than one communicating with
a VTL2 control plane. The host specifies this value based on the guest's configuration, and there is no other discovery
method available to determine the correct connection ID.

> So not suitable for DT. DT is a static data. You cannot just keep changing existing DT to match whatever you want runtime.

>From the guest's perspective, this data is completely static - it doesn't change over the lifetime of the guest.
The guest always looks it up in DT. The hypervisor merely populates this value in the guest's DT. Once set, it remains
fixed for that guest instance, so this data is not dynamic, it's completely fixed for the guest.




Thanks,
Hardik