From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alex Williamson <alex.williamson@redhat.com>
Subject: Re: pci passthrough - VF reset at boot is dropping assigned MAC
Date: Mon, 25 Apr 2011 12:36:34 -0600
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To: David Ahern <dsahern@gmail.com>
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On Mon, 2011-04-25 at 12:04 -0600, David Ahern wrote:
> 
> On 04/25/11 11:30, Alex Williamson wrote:
> > # modprobe -r igbvf
> > # ip link set eth2 vf 6 mac 02:00:10:91:73:01
> > # modprobe igbvf
> > # dmesg | grep "igbvf 0000\:01\:11.5\: Address\:"
> > igbvf 0000:01:11.5: Address: d2:c8:17:d6:97:f7
> > igbvf 0000:01:11.5: Address: 4e:ee:2a:d8:12:7c
> > igbvf 0000:01:11.5: Address: 02:00:10:91:73:01
> > # modprobe -r igbvf
> > # echo 1 > /sys/bus/pci/devices/0000:01:11.5/reset
> > # modprobe igbvf
> > # dmesg | grep "igbvf 0000\:01\:11.5\: Address\:"
> > igbvf 0000:01:11.5: Address: d2:c8:17:d6:97:f7
> > igbvf 0000:01:11.5: Address: 4e:ee:2a:d8:12:7c
> > igbvf 0000:01:11.5: Address: 02:00:10:91:73:01
> > igbvf 0000:01:11.5: Address: 02:00:10:91:73:01
> > 
> > So now it sticks.  You're going to get random mac addresses on the VFs
> > every time you reload the igb driver (ie. ever boot) anyway (at least
> > with these sr-iov cards), so if you need consistent macs, they probably
> > need to be set before launching the VM anyway.  Thanks,
> > 
> > Alex
> > 
> 
> Ok, I was able to repeat the above commands from the host command line.
> 
> However, when qemu-kvm starts the MAC is reset.
> 
> # ip link show | less
> 
> 2: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP
> qlen 1000
>     link/ether 00:1b:21:98:b7:10 brd ff:ff:ff:ff:ff:ff
>     vf 0 MAC 02:12:34:56:80:20
> 
> --> that's the MAC address I set
> 
> I start qemu-kvm (unpatched version) and the host side sees the address
> changed:
> 
> # ip link show | less
> 
> 2: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP
> qlen 1000
>     link/ether 00:1b:21:98:b7:10 brd ff:ff:ff:ff:ff:ff
>     vf 0 MAC 7a:17:3f:98:0f:db
> 
> 
> Can you try that aspect on your end - seeing if the MAC address
> maintains after starting qemu-kvm?

I don't see this happening on my system, once manually set the mac never
changes.  I can restart and reset the VM and the host and guest both
continue seeing the set mac address.  I tested it with both a recent
rhel6.1 host kernel as well as upstream 2.6.39-rc4.  If I switch to a VF
with an unset mac, those will change on each VM reset or restart.
Thanks,

Alex