From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37772) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fY3pE-00042y-1T for qemu-devel@nongnu.org; Wed, 27 Jun 2018 02:21:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fY3pD-0007LX-04 for qemu-devel@nongnu.org; Wed, 27 Jun 2018 02:21:08 -0400 Received: from mail-it0-x242.google.com ([2607:f8b0:4001:c0b::242]:51035) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1fY3pC-0007KL-K6 for qemu-devel@nongnu.org; Wed, 27 Jun 2018 02:21:06 -0400 Received: by mail-it0-x242.google.com with SMTP id u4-v6so5847263itg.0 for ; Tue, 26 Jun 2018 23:21:06 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20180627032825-mutt-send-email-mst@kernel.org> References: <20180623002628-mutt-send-email-mst@kernel.org> <20180623012406-mutt-send-email-mst@kernel.org> <20180626044650-mutt-send-email-mst@kernel.org> <20180627032825-mutt-send-email-mst@kernel.org> From: Siwei Liu Date: Tue, 26 Jun 2018 23:21:04 -0700 Message-ID: Content-Type: text/plain; charset="UTF-8" Subject: Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: "Samudrala, Sridhar" , Cornelia Huck , Alexander Duyck , virtio-dev@lists.oasis-open.org, aaron.f.brown@intel.com, Jiri Pirko , Jakub Kicinski , Netdev , qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, Joao Martins , Venu Busireddy , vijay.balakrishna@oracle.com On Tue, Jun 26, 2018 at 5:29 PM, Michael S. Tsirkin wrote: > On Tue, Jun 26, 2018 at 04:38:26PM -0700, Siwei Liu wrote: >> On Mon, Jun 25, 2018 at 6:50 PM, Michael S. Tsirkin wrote: >> > On Mon, Jun 25, 2018 at 10:54:09AM -0700, Samudrala, Sridhar wrote: >> >> > > > > Might not neccessarily be something wrong, but it's very limited to >> >> > > > > prohibit the MAC of VF from changing when enslaved by failover. >> >> > > > You mean guest changing MAC? I'm not sure why we prohibit that. >> >> > > I think Sridhar and Jiri might be better person to answer it. My >> >> > > impression was that sync'ing the MAC address change between all 3 >> >> > > devices is challenging, as the failover driver uses MAC address to >> >> > > match net_device internally. >> >> >> >> Yes. The MAC address is assigned by the hypervisor and it needs to manage the movement >> >> of the MAC between the PF and VF. Allowing the guest to change the MAC will require >> >> synchronization between the hypervisor and the PF/VF drivers. Most of the VF drivers >> >> don't allow changing guest MAC unless it is a trusted VF. >> > >> > OK but it's a policy thing. Maybe it's a trusted VF. Who knows? >> > For example I can see host just >> > failing VIRTIO_NET_CTRL_MAC_ADDR_SET if it wants to block it. >> > I'm not sure why VIRTIO_NET_F_STANDBY has to block it in the guest. >> >> That's why I think pairing using MAC is fragile IMHO. When VF's MAC >> got changed before virtio attempts to match and pair the device, it >> ends up with no pairing found out at all. > > Guest seems to match on the hardware mac and ignore whatever > is set by user. Makes sense to me and should not be fragile. Host can change the hardware mac for VF any time. -Siwei > > >> UUID is better. >> >> -Siwei >> >> > >> > -- >> > MST