From nobody Sun Feb 8 03:32:59 2026 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 4062F2D97AC; Tue, 23 Dec 2025 23:07:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766531246; cv=none; b=NB/Kh43HXnyyQ3SLGArIc8SVGD0OLEWds4TCji9ntnnRBMQ7ktHBoqSY+Ip+39QI1lzLzYazvQWPdyqPvfOtr9T6J3zPak/RDGJKiEAS0HBQY9ey5Zo58PDrj6ZgpEqjjN7HIYsRwgMHSK44n8l0nf1VefZJR1YtdIg/+5mhX14= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766531246; c=relaxed/simple; bh=p4Vim08FZY9jFjXJAON9DOs70JPSNCDFirXt+o6YuZU=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=c26EBgXpn+gmdJQYiaB9XfBUEF7P36Y5mJ4dowNtTNM6FDmY7fuB/MC9FGdfcj0pnCZyhdLT1gQiPH/93NYpK3CGnVITAh6FaCuRRHk09AiXpl3+WNEwdtxsLks9OPqWwFPod8AKS8hdeuSrHD06OJyGt5Athqo2/aQs/c3M/+I= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=rjBI2ba3; arc=none smtp.client-ip=13.77.154.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="rjBI2ba3" Received: from [100.65.0.124] (unknown [20.236.10.206]) by linux.microsoft.com (Postfix) with ESMTPSA id 24F85212A423; Tue, 23 Dec 2025 15:07:24 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 24F85212A423 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1766531244; bh=p4Vim08FZY9jFjXJAON9DOs70JPSNCDFirXt+o6YuZU=; h=Date:Subject:From:To:Cc:References:In-Reply-To:From; b=rjBI2ba38RfTtEu5BbW0kliCcvjdRDZn23LebTve+rriaXtKHUwweXK1ufb9SN3oR 8JYF2egfQA8WfvpHErFhRijLanLhcXu5bc6b9FTj8iAd2WEz1cllsopr3s7vktmNfM pzmi4i3eYsbkDLvjtBWhAtoJMKzkxdk1Ui8X5Wco= Message-ID: <3fe6a9a3-b6e2-4550-b2a9-924b1fca21b5@linux.microsoft.com> Date: Tue, 23 Dec 2025 15:07:22 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: [PATCH v5 1/2] dt-bindings: microsoft: Add vmbus message-connection-id property From: Hardik Garg To: kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, krzk+dt@kernel.org, robh@kernel.org, conor+dt@kernel.org, mhklinux@outlook.com Cc: devicetree@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, ssengar@linux.microsoft.com, longli@microsoft.com, Naman Jain , hargar@microsoft.com References: <58cb22cb-b0c8-4694-b9e4-971aa7f0f972@linux.microsoft.com> Content-Language: en-US In-Reply-To: <58cb22cb-b0c8-4694-b9e4-971aa7f0f972@linux.microsoft.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Document the microsoft,message-connection-id property for VMBus DeviceTree node. The connection-id is a hardware-level identifier that specifies which Hyper-V message port (or mailbox slot) the guest should use to communicate with the VMBus control plane. Historically, VMBus always used a single, fixed connection ID. However, with the introduction of Virtual Trust Level 2 (VTL2) support, the control plane can now reside in a different trust level, requiring the guest to communicate through a different message port. This connection-id is determined by the hypervisor based on the status of VMBus relay. From the guests perspective, it is completely static for the lifetime of that VM instance, it never changes at runtime. Once the kernel boots, it must read this value to establish communication with the correct VMBus control plane. There is currently no system API, or discoverable interface that allows the guest to determine this value dynamically. Each guest has a private hypervisor mailbox and cannot access any other guests 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. Signed-off-by: Hardik Garg --- v4: https://lore.kernel.org/all/1750374395-14615-2-git-send-email-hargar@linux.= microsoft.com v3: https://lore.kernel.org/all/6a92ca86-ad6b-4d49-af6e-1ed7651b8ab8@linux.micr= osoft.com v2: https://lore.kernel.org/all/096edaf7-cc90-42b6-aff4-c5f088574e1e@linux.micr= osoft.com v1: https://lore.kernel.org/all/6acee4bf-cb04-43b9-9476-e8d811d26dfd@linux.micr= osoft.com --- =C2=A0.../devicetree/bindings/bus/microsoft,vmbus.yaml=C2=A0 =C2=A0 =C2=A0|= 12 ++++++++++++ =C2=A01 file changed, 12 insertions(+) diff --git a/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml b/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml index 0bea4f5287ce..4745c2b89ac5 100644 --- a/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml +++ b/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml @@ -17,6 +17,17 @@ properties: =C2=A0 =C2=A0compatible: =C2=A0 =C2=A0 =C2=A0const: microsoft,vmbus =C2=A0 +=C2=A0 microsoft,message-connection-id: +=C2=A0 =C2=A0 description: +=C2=A0 =C2=A0 =C2=A0 connection-id is a hardware-level identifier that spe= cifies +=C2=A0 =C2=A0 =C2=A0 which Hyper-V message port (or mailbox slot) the gues= t should +=C2=A0 =C2=A0 =C2=A0 use to communicate with the VMBus control plane. When= this +=C2=A0 =C2=A0 =C2=A0 property is not present, the driver selects the conne= ction ID +=C2=A0 =C2=A0 =C2=A0 based on the protocol version (4 for VERSION_WIN10_V5= and +=C2=A0 =C2=A0 =C2=A0 newer, or 1 for older versions). +=C2=A0 =C2=A0 $ref: /schemas/types.yaml#/definitions/uint32 +=C2=A0 =C2=A0 minimum: 1 + =C2=A0 =C2=A0ranges: true =C2=A0 =C2=A0 =C2=A0'#address-cells': @@ -55,6 +66,7 @@ examples: =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0vmbus@ff0000000 { =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0compatible = =3D "microsoft,vmbus"; +=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 microsoft,message-= connection-id =3D <4>; =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0#address-cell= s =3D <2>; =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0#size-cells = =3D <1>; =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0ranges =3D <0= x0f 0xf0000000 0x0f 0xf0000000 0x10000000>; --=C2=A0 2.34.1