From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50963) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1faMf6-0005Au-DO for qemu-devel@nongnu.org; Tue, 03 Jul 2018 10:52:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1faMf5-0008WG-D6 for qemu-devel@nongnu.org; Tue, 03 Jul 2018 10:52:12 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:50280 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1faMf5-0008TC-7F for qemu-devel@nongnu.org; Tue, 03 Jul 2018 10:52:11 -0400 Date: Tue, 3 Jul 2018 16:52:00 +0200 From: Cornelia Huck Message-ID: <20180703165200.180c93bb.cohuck@redhat.com> In-Reply-To: <20180703142817.GA3088@vbusired-vm> References: <20180629221907.3662-1-venu.busireddy@oracle.com> <20180702161404.GA2339@rkaganb.sw.ru> <449f1449-ddf6-cd95-976c-14d04d8d503a@oracle.com> <20180703095825.GC30904@rkaganb.sw.ru> <20180703142817.GA3088@vbusired-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [virtio-dev] Re: [PATCH v3 0/3] Use of unique identifier for pairing virtio and passthrough devices... List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Venu Busireddy Cc: Roman Kagan , si-wei liu , "Michael S . Tsirkin" , Marcel Apfelbaum , virtio-dev@lists.oasis-open.org, qemu-devel@nongnu.org On Tue, 3 Jul 2018 09:28:17 -0500 Venu Busireddy wrote: > On 2018-07-03 12:58:25 +0300, Roman Kagan wrote: > > On Mon, Jul 02, 2018 at 02:14:52PM -0700, si-wei liu wrote: =20 > > > On 7/2/2018 9:14 AM, Roman Kagan wrote: =20 > > > > Is the scheme going to be applied/extended to other transports (vmb= us, > > > > virtio-ccw, etc.)? =20 > > > Well, it depends on the use case, and how feasible it can be extended= to > > > other transport due to constraints and transport specifics. > > > =20 > > > > Is the failover group concept going to be used beyond PT-PV network > > > > device failover? =20 > > > Although the concept of failover group is generic, the implementation= itself > > > may vary. =20 > >=20 > > My point with these two questions is that since this patchset is > > defining external interfaces -- with guest OS, with management layer --= =20 >=20 > This patch set is not defining any external interfaces. All this is doing > is provide the means and locations to store the "group identifier". How > that info will be used, I thought, should be another patch set. >=20 > Venu >=20 > > which are not easy to change later, it might make sense to try and see > > if the interfaces map to other usecases. E.g. I think we can get enough > > information on how Hyper-V handles PT-PV network device failover from > > the current Linux implementation; it may be a good idea to share some > > concepts and workflows with virtio-pci. But this patch set defines a host<->guest interface to make pairing information on the host available to the guest, no? =46rom my point of view, there are several concerns: - This approach assumes a homogeneous pairing (same transport), and even more, it assumes that this transport is pci. - It won't work for zPCI (although zPCI is really strange) -- this means it will be completely unusable on s390x. - It is too focused on a narrow use case. How is it supposed to be extended? What I would prefer: - Implement a pairing id support that does not rely on a certain transport, but leverages virtio (which is in the game anyway). We'd get at least the "virtio-net device paired with vfio" use case, which is what is currently implemented in the Linux kernel. - Think about a more generic way to relay configuration metadata to the host.