From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Samudrala, Sridhar" Subject: Re: [PATCH net-next v9 3/4] virtio_net: Extend virtio to use VF datapath when available Date: Sun, 29 Apr 2018 20:00:33 -0700 Message-ID: <62f3b81b-70f6-6991-8e23-2bf650ecea2d@intel.com> References: <1524848820-42258-1-git-send-email-sridhar.samudrala@intel.com> <1524848820-42258-4-git-send-email-sridhar.samudrala@intel.com> <20180428082433.GK5632@nanopsycho.orion> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: mst@redhat.com, stephen@networkplumber.org, davem@davemloft.net, netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, virtio-dev@lists.oasis-open.org, jesse.brandeburg@intel.com, alexander.h.duyck@intel.com, kubakici@wp.pl, jasowang@redhat.com, loseweigh@gmail.com, aaron.f.brown@intel.com To: Jiri Pirko Return-path: Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: In-Reply-To: <20180428082433.GK5632@nanopsycho.orion> Content-Language: en-US List-Id: netdev.vger.kernel.org On 4/28/2018 1:24 AM, Jiri Pirko wrote: > Fri, Apr 27, 2018 at 07:06:59PM CEST, sridhar.samudrala@intel.com wrote: >> This patch enables virtio_net to switch over to a VF datapath when a VF >> netdev is present with the same MAC address. It allows live migration >> of a VM with a direct attached VF without the need to setup a bond/team >> between a VF and virtio net device in the guest. >> >> The hypervisor needs to enable only one datapath at any time so that >> packets don't get looped back to the VM over the other datapath. When a VF > Why? Both datapaths could be enabled at a time. Why the loop on > hypervisor side would be a problem. This in not an issue for > bonding/team as well. Somehow the hypervisor needs to make sure that the broadcasts/multicasts from the VM sent over the VF datapath don't get looped back to the VM via the virtio-net datapth. This can happen if both datapaths are enabled at the same time. I would think this is an issue even with bonding/team as well when virtio-net and VF are backed by the same PF. > > >> is plugged, the virtio datapath link state can be marked as down. The >> hypervisor needs to unplug the VF device from the guest on the source host >> and reset the MAC filter of the VF to initiate failover of datapath to > "reset the MAC filter of the VF" - you mean "set the VF mac"? Yes.  the PF should take away the MAC address assigned to the VF so that the PF starts receiving those packets. > > >> virtio before starting the migration. After the migration is completed, >> the destination hypervisor sets the MAC filter on the VF and plugs it back >> to the guest to switch over to VF datapath. >> >> It uses the generic failover framework that provides 2 functions to create >> and destroy a master failover netdev. When STANDBY feature is enabled, an >> additional netdev(failover netdev) is created that acts as a master device >> and tracks the state of the 2 lower netdevs. The original virtio_net netdev >> is marked as 'standby' netdev and a passthru device with the same MAC is >> registered as 'primary' netdev. >> >> This patch is based on the discussion initiated by Jesse on this thread. >> https://marc.info/?l=linux-virtualization&m=151189725224231&w=2 > [...] >