Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Dexuan Cui <decui@microsoft.com>
To:     kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com,
        sashal@kernel.org, linux-hyperv@vger.kernel.org,
        linux-kernel@vger.kernel.org, mikelley@microsoft.com,
        Alexander.Levin@microsoft.com
Cc:     sunilmut@microsoft.com, Andrea.Parri@microsoft.com,
        Dexuan Cui <decui@microsoft.com>
Subject: [PATCH] Drivers: hv: vmbus: Ignore CHANNELMSG_TL_CONNECT_RESULT(23)
Date:   Thu,  9 Jan 2020 17:25:15 -0800
Message-Id: <1578619515-115811-1-git-send-email-decui@microsoft.com>
Reply-To: decui@microsoft.com
Content-Type: text/plain
MIME-Version: 1.0
Received-SPF: None (protection.outlook.com: microsoft.com does not designate
 permitted sender hosts)
X-MS-Exchange-CrossTenant-Network-Message-Id: a0a26289-b1d6-4845-587c-08d7956c01c2
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Jan 2020 01:25:41.9103
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 72f988bf-86f1-41af-91ab-2d7cd011db47
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: 7EQ8BpjH4wIW936CWUYqUfXB8NIhwSGXKam3a+TCBxH8oL8vKoLAmBvVfyn0XBVUSvTGDZrEkZHBPivWz5KlIQ==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR21MB0858
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

When a Linux hv_sock app tries to connect to a Service GUID on which no
host app is listening, a recent host (RS3+) sends a
CHANNELMSG_TL_CONNECT_RESULT (23) message to Linux and this triggers such
a warning:

unknown msgtype=23
WARNING: CPU: 2 PID: 0 at drivers/hv/vmbus_drv.c:1031 vmbus_on_msg_dpc

Actually Linux can safely ignore the message because the Linux app's
connect() will time out in 2 seconds: see VSOCK_DEFAULT_CONNECT_TIMEOUT
and vsock_stream_connect(). We don't bother to make use of the message
because: 1) it's only supported on recent hosts; 2) a non-trivial effort
is required to use the message in Linux, but the benefit is small.

So, let's not see the warning by silently ignoring the message.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
---
 drivers/hv/vmbus_drv.c | 5 +++++
 include/linux/hyperv.h | 2 ++
 2 files changed, 7 insertions(+)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 4ef5a66df680..c838b6f5f726 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1033,6 +1033,11 @@ void vmbus_on_msg_dpc(unsigned long data)
 	}
 
 	entry = &channel_message_table[hdr->msgtype];
+
+	/* Linux ignores some messages, e.g. CHANNELMSG_TL_CONNECT_RESULT. */
+	if (!entry->message_handler)
+		goto msg_handled;
+
 	if (entry->handler_type	== VMHT_BLOCKING) {
 		ctx = kmalloc(sizeof(*ctx), GFP_ATOMIC);
 		if (ctx == NULL)
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 26f3aeeae1ca..41c58011431e 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -425,6 +425,8 @@ enum vmbus_channel_message_type {
 	CHANNELMSG_19				= 19,
 	CHANNELMSG_20				= 20,
 	CHANNELMSG_TL_CONNECT_REQUEST		= 21,
+	CHANNELMSG_22				= 22,
+	CHANNELMSG_TL_CONNECT_RESULT		= 23,
 	CHANNELMSG_COUNT
 };
 
-- 
2.19.1