netdev - Re: [PATCH net-next v9 3/4] virtio_net: Extend virtio to use VF datapath when available

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Date:   Sat, 28 Apr 2018 11:42:05 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Sridhar Samudrala <sridhar.samudrala@...el.com>
Cc:     mst@...hat.com, stephen@...workplumber.org, davem@...emloft.net,
        netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        virtio-dev@...ts.oasis-open.org, jesse.brandeburg@...el.com,
        alexander.h.duyck@...el.com, kubakici@...pl, jasowang@...hat.com,
        loseweigh@...il.com, aaron.f.brown@...el.com
Subject: Re: [PATCH net-next v9 3/4] virtio_net: Extend virtio to use VF
 datapath when available

Fri, Apr 27, 2018 at 07:06:59PM CEST, sridhar.samudrala@...el.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
>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
>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
>

When I enabled the standby feature (hardcoded), I have 2 netdevices now:
4: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 52:54:00:b2:a7:f1 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::5054:ff:feb2:a7f1/64 scope link 
       valid_lft forever preferred_lft forever
5: ens3n_sby: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 52:54:00:b2:a7:f1 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::5054:ff:feb2:a7f1/64 scope link 
       valid_lft forever preferred_lft forever

However, it seems to confuse my initscripts on Fedora:
[root@...t1 ~]# ifup ens3
./network-functions: line 78: [: /etc/dhcp/dhclient-ens3: binary operator expected
./network-functions: line 80: [: /etc/dhclient-ens3: binary operator expected
./network-functions: line 69: [: /var/lib/dhclient/dhclient-ens3: binary operator expected

Determining IP information for ens3
ens3n_sby...Cannot find device "ens3n_sby.pid"
Cannot find device "ens3n_sby.lease"
 failed.

I tried to change the standby device mac:
ip link set ens3n_sby addr 52:54:00:b2:a7:f2
[root@...t1 ~]# ifup ens3

Determining IP information for ens3... done.
[root@...t1 ~]#

But now the network does not work. I think that the mac change on
standby device should be probably refused, no?

When I change the mac back, all works fine.


Now I try to change mac of the failover master:
[root@...t1 ~]# ip link set ens3 addr 52:54:00:b2:a7:f3
RTNETLINK answers: Operation not supported

That I did expect to work. I would expect this would change the mac of
the master and both standby and primary slaves.


Now I tried to add a primary pci device. I don't have any fancy VF on my
test setup, but I expected the good old 8139cp to work:
[root@...t1 ~]# ethtool -i ens9
driver: 8139cp
....
[root@...t1 ~]# ip link set ens9 addr 52:54:00:b2:a7:f1

I see no message in dmesg, so I guess the failover module did not
enslave this netdev. The mac change is not monitored. I would expect
that it is and whenever a device changes mac to the failover one, it
should be enslaved and whenever it changes mac back to something else,
it should be released - the primary one ofcourse.



[...]

>+static int virtnet_get_phys_port_name(struct net_device *dev, char *buf,
>+				      size_t len)
>+{
>+	struct virtnet_info *vi = netdev_priv(dev);
>+	int ret;
>+
>+	if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_STANDBY))
>+		return -EOPNOTSUPP;
>+
>+	ret = snprintf(buf, len, "_sby");

please avoid the "_".

[...]