From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41212) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fdh6S-0008GH-QL for qemu-devel@nongnu.org; Thu, 12 Jul 2018 15:18:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fdh6N-0000wy-OM for qemu-devel@nongnu.org; Thu, 12 Jul 2018 15:18:12 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:47046 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 1fdh6N-0000wA-Iu for qemu-devel@nongnu.org; Thu, 12 Jul 2018 15:18:07 -0400 Date: Thu, 12 Jul 2018 22:18:04 +0300 From: "Michael S. Tsirkin" Message-ID: <20180712160211-mutt-send-email-mst@kernel.org> 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> <20180709130035.GA6271@rkaganb.sw.ru> <9136094e-a510-4201-7c71-d1c49226fa5f@oracle.com> <20180710045101-mutt-send-email-mst@kernel.org> <20180711115344.633eba9e.cohuck@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180711115344.633eba9e.cohuck@redhat.com> 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: Cornelia Huck Cc: Siwei Liu , si-wei liu , Roman Kagan , Venu Busireddy , Marcel Apfelbaum , virtio-dev@lists.oasis-open.org, qemu-devel@nongnu.org, "Samudrala, Sridhar" , Alexander Duyck , Netdev On Wed, Jul 11, 2018 at 11:53:44AM +0200, Cornelia Huck wrote: > On Tue, 10 Jul 2018 17:07:37 -0700 > Siwei Liu wrote: > > > On Mon, Jul 9, 2018 at 6:54 PM, Michael S. Tsirkin wrote: > > > On Mon, Jul 09, 2018 at 06:11:53PM -0700, si-wei liu wrote: > > >> The plan is to enable group ID based matching in the first place rather than > > >> match by MAC, the latter of which is fragile and problematic. > > > > > > It isn't all that fragile - hyperv used same for a while, so if someone > > > posts working patches with QEMU support but before this grouping stuff, > > > I'll happily apply them. > > > > I wouldn't box the solution to very limited scenario just because of > > matching by MAC, the benefit of having generic group ID in the first > > place is that we save the effort of maintaining legacy MAC based > > pairing that just adds complexity anyway. Currently the VF's MAC > > address cannot be changed by either PF or by the guest user is a > > severe limitation due to this. The other use case is that PT device > > than VF would generally have different MAC than the standby virtio. We > > shouldn't limit itself to VF specific scenario from the very > > beginning. > > So, this brings me to a different concern: the semantics of > VIRTIO_NET_F_STANDBY. > > * The currently sole user seems to be the virtio-net Linux driver. > * The commit messages, code comments and Documentation/ all talk about > matching by MAC. > * I could not find any proposed update to the virtio spec. (If there > had been an older proposal with a different feature name, it is not > discoverable.) > > VIRTIO_NET_F_STANDBY is a host <-> guest interface. As there's no > official spec, you can only go by the Linux implementation, and by that > its semantics seem to be 'match by MAC', not 'match by other criteria'. > > How is this supposed to work in the long run? We definitely need a spec patch for VIRTIO_NET_F_STANDBY documenting existing semantics. Sridhar, do you plan to take a look? -- MST