From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MJWnH-0007yT-EE for qemu-devel@nongnu.org; Wed, 24 Jun 2009 14:01:59 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MJWnC-0007pa-TO for qemu-devel@nongnu.org; Wed, 24 Jun 2009 14:01:58 -0400 Received: from [199.232.76.173] (port=35941 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MJWnC-0007pN-G8 for qemu-devel@nongnu.org; Wed, 24 Jun 2009 14:01:54 -0400 Received: from mx2.redhat.com ([66.187.237.31]:34682) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1MJWnB-0005QI-QU for qemu-devel@nongnu.org; Wed, 24 Jun 2009 14:01:54 -0400 Date: Wed, 24 Jun 2009 23:31:14 +0530 From: Amit Shah Subject: Re: [Qemu-devel] virtio-serial: A guest <-> host interface for simple communication Message-ID: <20090624180114.GA24906@amit-x200.redhat.com> References: <1245760953-32139-1-git-send-email-amit.shah@redhat.com> <20090624164049.GE14121@shareable.org> <20090624170632.GA24285@amit-x200.redhat.com> <20090624175002.GJ14121@shareable.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090624175002.GJ14121@shareable.org> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jamie Lokier Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org On (Wed) Jun 24 2009 [18:50:02], Jamie Lokier wrote: > Amit Shah wrote: > > On (Wed) Jun 24 2009 [17:40:49], Jamie Lokier wrote: > > > Amit Shah wrote: > > > > A few sample uses for a vmchannel are to share the host and guest > > > > clipboards (to allow copy/paste between a host and a guest), to > > > > lock the screen of the guest session when the vnc viewer is closed, > > > > to find out which applications are installed on a guest OS even when > > > > the guest is powered down (using virt-inspector) and so on. > > > > > > Those all look like useful features. > > > > > > Can you run an application to provide those features on a guest which > > > _doesn't_ have a vmchannel/virtio-serial support in the kernel? > > > > > > Or will it be restricted only to guests which have QEMU-specific > > > support in their kernel? > > > > libguestfs currently uses the -net user based vmchannel interface that > > exists in current qemu. That doesn't need a kernel that doesn't have > > support for virtio-serial. > > That's great! > > If that works fine, and guest apps/libraries are using that as a > fallback anyway, what benefit do they get from switching to > virtio-serial when they detect that instead, given they still have > code for the -net method? Speed is the biggest benefit. > Is the plan to remove -net user based support from libguestfs? I don't know what Richard's plan is, but if the kernel that libguestfs deploys in the appliance gains support for virtio-serial, there's no reason it shouldn't switch. > Is virtio-serial significantly simpler to use? I think the interface from the guest POV stays the same: reads / writes to char devices. With virtio-serial, though, we can add a few other interesting things like names to ports, ability to hot-add ports on demand, request notifications when either end goes down, etc. Amit