From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MJgnF-0004LG-Je for qemu-devel@nongnu.org; Thu, 25 Jun 2009 00:42:37 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MJgnB-0004Ky-TJ for qemu-devel@nongnu.org; Thu, 25 Jun 2009 00:42:37 -0400 Received: from [199.232.76.173] (port=51647 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MJgnB-0004Kv-Ms for qemu-devel@nongnu.org; Thu, 25 Jun 2009 00:42:33 -0400 Received: from mx2.redhat.com ([66.187.237.31]:60949) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1MJgnB-0008NK-8t for qemu-devel@nongnu.org; Thu, 25 Jun 2009 00:42:33 -0400 Date: Thu, 25 Jun 2009 10:11:57 +0530 From: Amit Shah Subject: Re: [Qemu-devel] virtio-serial: A guest <-> host interface for simple communication Message-ID: <20090625044157.GB26664@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> <20090624180114.GA24906@amit-x200.redhat.com> <20090624192027.GT14121@shareable.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090624192027.GT14121@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 [20:20:27], Jamie Lokier wrote: > Amit Shah wrote: > > > > 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. > > Good features, useful for a lot of handy things. I think it would be > handy if the same features were available to the guest application > generally, not just on guest kernels with a specific driver though. > > As we talked before, about things like boot loaders and kernel > debuggers, and installing the support applications on old guests. The -net vmchannel offers that option. Can't see how to do it other way. > Is it possible to support access to the same capabilities through a > well known IO/MMIO address, in the same way that VGA and IDE are both > ordinary PCI devices, but also can be reached easily through well > known IO/MMIO addresses in simple code? The exits caused by accessing IO/MMIO regions are costlier than using PV. So using the current vmchannel option would be almost similar in those respects. Also, virtio is the almost standard way these days to get performance. We already have block, net drivers over virtio and they have been ported to older kernels as well. Amit