From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42470) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gPVFb-0004JW-H6 for qemu-devel@nongnu.org; Wed, 21 Nov 2018 11:21:16 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gPVFY-0006B1-21 for qemu-devel@nongnu.org; Wed, 21 Nov 2018 11:21:15 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60462) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gPVFX-00069M-Qb for qemu-devel@nongnu.org; Wed, 21 Nov 2018 11:21:12 -0500 Message-ID: From: Andrea Bolognani Date: Wed, 21 Nov 2018 17:20:41 +0100 In-Reply-To: <20181120140251-mutt-send-email-mst@kernel.org> References: <20181114233831.10374-1-ehabkost@redhat.com> <20181116034551.GK3807@habkost.net> <20181119114105.4da89f2c.cohuck@redhat.com> <20181119125519-mutt-send-email-mst@kernel.org> <20181119193238.117c2f4e.cohuck@redhat.com> <20181119133434-mutt-send-email-mst@kernel.org> <20181119195638.49a9c21e.cohuck@redhat.com> <20181119140813-mutt-send-email-mst@kernel.org> <9bc6ced6b0491643775081b8f8437065684e9959.camel@redhat.com> <20181120140251-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH for-4.0 v2] virtio: Provide version-specific variants of virtio PCI devices List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Cornelia Huck , Eduardo Habkost , qemu-devel@nongnu.org, Gonglei , Paolo Bonzini , Amit Shah , Cleber Rosa , Marcel Apfelbaum , Fam Zheng , Kevin Wolf , Max Reitz , Jason Wang , Wainer dos Santos Moschetta , Philippe =?ISO-8859-1?Q?Mathieu-Daud=E9?= , libvir-list@redhat.com, Markus Armbruster , Laine Stump , Stefan Hajnoczi , Gerd Hoffmann , "Daniel P. =?ISO-8859-1?Q?Berrang=E9?=" , Caio Carrara On Tue, 2018-11-20 at 14:14 -0500, Michael S. Tsirkin wrote: > On Tue, Nov 20, 2018 at 01:27:05PM +0100, Andrea Bolognani wrote: > > On Mon, 2018-11-19 at 14:14 -0500, Michael S. Tsirkin wrote: > > > Well it works now - connect it to a bus and it figures out whether it > > > should do transitional or not. You can force transitional in PCIe anyway > > > but then you are limited to about 15 devices - probably sufficient for > > > most people ... > > > > That's not how it works, though: current virtio-*-pci devices will > > be transitional (and thus support older guest OS) or not based on > > the kind of slot you plug them into. > > > > From the management point of view that's problematic, because libvirt > > (which takes care of the virtual hardware, including assigning PCI > > addresses to devices) has no knowledge of the guest OS running on > > said hardware, and management apps (which know about the guest OS and > > can figure out its capabilities using libosinfo) don't want to be in > > the business of assigning PCI addresses themselves. > > > > Having separate transitional and non-transitional variants solves the > > issue because now management apps can query libosinfo to figure out > > whether the guest OS supports non-transitional virtio devices, and > > based on that they can ask libvirt to use either the transitional or > > non-transitional variant; from that, libvirt will be able to choose > > the correct slot for the device. > > > > None of the above quite works if we have a single variant that > > morphs based on the slot, as we have today. > > So can we get an ack on the patchset then? Sure thing - whatever it might be worth :) Acked-by: Andrea Bolognani -- Andrea Bolognani / Red Hat / Virtualization