From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MM6rE-00037P-6m for qemu-devel@nongnu.org; Wed, 01 Jul 2009 16:56:44 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MM6r9-00033G-Nq for qemu-devel@nongnu.org; Wed, 01 Jul 2009 16:56:43 -0400 Received: from [199.232.76.173] (port=41756 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MM6r9-000334-D1 for qemu-devel@nongnu.org; Wed, 01 Jul 2009 16:56:39 -0400 Received: from mx2.redhat.com ([66.187.237.31]:50215) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1MM6r9-0008V4-2x for qemu-devel@nongnu.org; Wed, 01 Jul 2009 16:56:39 -0400 Message-ID: <4A4BCD80.2000906@redhat.com> Date: Wed, 01 Jul 2009 22:56:32 +0200 From: Gerd Hoffmann MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH 0/2] Tunnel character device data over VNC (v1) References: <20090701162114.GB24296@redhat.com> <4A4B91F7.9010206@redhat.com> <20090701165039.GF24296@redhat.com> <4A4B9D2F.5000607@redhat.com> <4A4BB038.7050401@codemonkey.ws> <4A4BBBE6.2070601@redhat.com> <4A4BC01B.7000100@codemonkey.ws> In-Reply-To: <4A4BC01B.7000100@codemonkey.ws> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: qemu-devel@nongnu.org On 07/01/09 21:59, Anthony Liguori wrote: > Gerd Hoffmann wrote: >> Monitor is a special case. Multiple connections to the same session >> are not very useful there. Multiple sessions are a different (albeit >> related) problem. > > Serial is the same. Imagine a bash shell running on the serial port with > two VNC client connected and stdio connected. Utter chaos. You really > want to use one or the other, never both at the same time. Typing to both at the same time isn't going to work well indeed. IMHO that isn't a reason to enforce one connection only though. It is still a useful feature. Use case: vm running at your workstation in the office, with -serial tcp. You are heading home, leaving telnet connected. At home you'll find you want to check something in your vm via vpn. With current qemu: You have to zap the telnet session somehow to be able to connect. With switching: You have to talk to the monitor to reconfigure things. With multiple connections and multiplexing: You'll just connect, type a few commands, disconnect, done. You'll even see what you have done when you come back to the office the next day. Also note that the vnc server accepts input from multiple clients as well, which can lead to simliar problems. Nobody wants to kill support for multiple clients just because of that, because in practice it isn't a issue. Monitor is different for two reasons: First, we could actually open a new session. That wouldn't work for serial as we can't hotplug a serial line into the guest on connect. Second, if the monitor is used by libvirt or some other management app a second connection to the same session is seriously harmful. cheers, Gerd