|
On 09/03/2016 11:08 AM, Moshe Levi
wrote:
-----Original Message----- From: sendmail [mailto:justsendmailnothingelse@xxxxxxxxx] On Behalf Of Laine Stump Sent: Thursday, September 01, 2016 5:59 PM To: Libvirt <libvir-list@xxxxxxxxxx> Cc: Moshe Levi <moshele@xxxxxxxxxxxx>; Edan David <edand@xxxxxxxxxxxx> Subject: Re: <interface type='direct'> On 09/01/2016 04:05 AM, Moshe Levi wrote:Hi, In OpenStack we have a port type macvtap. Mavtap port is just a tap device connected to VF. In Libvirt the guest xml look like <interface type='direct'> <mac address='fa:16:3e:b1:06:4e'/> <source dev='p1p6' mode='passthrough'/> <target dev='macvtap1'/> <model type='virtio'/> <driver name='vhost'/> <alias name='net0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> In the hypervisor we can see that the mac of the VF which is fa:16:3e:f3:9b:e8 - is set by OpenStack see [1] 9: ens3f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mqmaster ovs-system state UP mode DEFAULT group default qlen 1000 Look at the explanation in commit cb3fe38c and also https://bugzilla.redhat.com/show_bug.cgi?id=1113474 That commit switched from using a simple ioctl(SIOCSIFHWADDR) to the VF's netdev name, to using a netlink RTM_SETLINK message to the netdev of the *PF* for the given VF. This was done because the latter is the *only* way you can set the MAC address for a VF that you're going to assign to the guest with vfio device assignment, and once you've set the MAC address that way, future attempts to set the MAC address with ioctl(SIOCSIGHWADDR) result in failure and a kernel log like this: kernel: igb 0000:0e:00.1: VF 1 attempted to override administratively set MAC address kernel: Reload the VF driver to resume operationsLooking into the kernel, it appears that once the MAC address for a VF has been set via RTM_SETLINK, the igb driver (and I believe also the ixgbe driver, not sure about others) doesn't allow it to be changed via ioctl until the PF driver is reloaded (which can't realistically be done on an active system) But recently there was another report of the MAC address not getting set properly for macvtap passthrough mode when the device is an SRIOV VF (I can't find it in bugzilla, so it must have been an email to one of the lists) and when I tried it myself I found they were correct - in the output of "ip link show" the MAC address showed in the list of VFs under the PF is correctly modified, but it's not set properly in the VF's netdev instance - apparently the MAC addresses in the VF list aren't set in the VF's netdev immediately, they're just saved to be set *the next time the VF is re-bound to the VF netdev driver*. I think in the past the interface may have been in promiscuous mode so it didn't matter, but now it isn't? I'm not sure as I haven't had much time to investigate. Does that make any more sense now? Since I don't see a reasonably efficient way to get this to work, I need to make a patch to revert to the old behavior, and we'll then just have to tell people "If you do hostdev device assignment of VFs, then you can't later re- use the same device for macvtap passthrough mode". (actually, I *think* an alternative would be to unbind/rebind the host driver to the VF after setting the VF MAC address, but that seems a bit disruptive/extreme to work around a problem that is probably only seen in QE labs, but not in the real world (realistically, production systems likely use either hostdev or macvtap, and don't switch back and forth between them). A question - I notice you have the vlan set for the VF. Does *that* properly take effect? (it's set in the same manner as the MAC address, via a netlink command to set the VFINFO)I am not sure what you mean, but we set the vlan in OpenStack after we create the guest xml. What command do you use to set it? Do you use "ip link set $PF vf $VF# vlan $VLANID" ? I think that's what it's showing here: https://review.openstack.org/#/c/364121/1/nova/network/linux_net.py (I don't know my way around openstack code, but arrived at that page via clicking on links from a google search) In OpenStack we put the MAC of the VF and the vlan using iproute2. I just want to know if that should be the part of Libvirt setting mac/vlan or Libvirt just create the macvtap interface and we should put the mac/vlan? libvirt *should* do it. We have a WIP patch in OpenStack for setting also the mac for thenetdevice of the VF [2]. Just wanted to know that this is the correct approach.Can you confirm that setting the VF netdevice mac in OpenStack is a reasonable workaround for the newer Libvirt versions? If libvirt isn't getting the job done, and you can set it yourself, then that's a workaround. I don't know that I'd call it "reasaonable" though. If everybody puts in special code to workaround bugs in libvirt (which is apparently what's been done) rather than actually reporting the bug (what you're doing now - Thanks!) then we are tricked into thinking that either the code works, or that nobody is using it so it doesn't matter if it's broken. The *best* way of overcoming this problem is to fix libvirt so it does what it's supposed to do. It's possible we can make it work by adding some operation after we send the RTM_SETLINK (maybe unbind the VF from its netdev driver, then re-bind, but that seems so drastic and time consuming!), or maybe we'll have to revert to using ioctl(SIOCSIFHWADDR), but of course that will fail if the interface has been used for hostdev assignment since the last host reboot. It's interesting that openstack is apparently using the RTM_SETLINK method to set the mac address (afaik, that's what is used by the "ip link set $pf_ifname vf $vf_num mac $mac_addr vlan $vlanid" command that's shown in the bit of code from nova/network/linux_net.py at the link I posted above). |
-- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list