From: Dexuan Cui <decui@xxxxxxxxxxxxx> Sent: Thursday, January 9, 2020 5:25 PM
>
> 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@xxxxxxxxxxxxx>
> ---
> 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;
> +
FWIW, with this new check, all of the validity checks in vmbus_onmessage() are
redundant and could be removed. There's already a check here that ensures
msgtype won't be too big, and this new check ensures that message_handler is
not NULL.
> 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
> };
For completeness, I'd like to see the channel_message_table also updated
with these new entries so that everything stays in sync and is explicitly
defined.
Michael
>
> --
> 2.19.1
