From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] Re: virtio-serial: An interface for host-guest communication Date: Mon, 27 Jul 2009 18:44:28 -0500 Message-ID: <4A6E3BDC.8050101@codemonkey.ws> References: <1248717876-17630-1-git-send-email-amit.shah@redhat.com> <4A6E0C9E.10908@codemonkey.ws> <20090727203214.GG15020@redhat.com> <20090727204627.GA32432@shareable.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "Daniel P. Berrange" , Amit Shah , qemu-devel@nongnu.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org To: Jamie Lokier Return-path: Received: from mail-yx0-f190.google.com ([209.85.210.190]:63053 "EHLO mail-yx0-f190.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752187AbZG0Xti (ORCPT ); Mon, 27 Jul 2009 19:49:38 -0400 Received: by yxe28 with SMTP id 28so134125yxe.33 for ; Mon, 27 Jul 2009 16:49:37 -0700 (PDT) In-Reply-To: <20090727204627.GA32432@shareable.org> Sender: kvm-owner@vger.kernel.org List-ID: Jamie Lokier wrote: > With multiple X servers, there can be more than one currently logged in user. > > Same with multiple text consoles - that's more familiar. > > Which one owns /dev/vmch3? > For a VMM, copy/paste should work with whatever user has the active X session that's controlling the physical display. Yes, it could get complicated if we supported multiple video cards, but fortunately we don't :-) I really think you need to have a copy/paste daemon that allows multiple X sessions to connect to it and then that daemon can somehow determine who is the "active" session. This is part of the reason I've been pushing for a concrete example. All the signs here point to a privileged daemon that delegates to multiple users. I think just about any use-case will have a similar model. It really suggests that you need _one_ vmchannel that's exposed to userspace with a single userspace daemon that consumes it. You want the flexibility of a userspace daemon in determining how you multiplex and do security. I don't think it's something you want to bake into the userspace/kernel interface. And if you have a single daemon that serves vmchannel sessions, that daemon can make it transparent whether the session is going over /dev/ttyS0, a network device, /dev/hvc1, etc. Regards, Anthony Liguori