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Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1113474 When we set the MAC address of a network device as a part of setting up macvtap "passthrough" mode (where the domain has an emulated netdev connected to a host macvtap device that has exclusive use of the physical device, and sets the device MAC address to match its own, i.e. "<interface type='direct'> <source mode='passthrough' .../>"), we use ioctl(SIOCSIFHWADDR) giving it the name of that device. This is true even if it is an SRIOV Virtual Function (VF). But, when we are setting the MAC address / vlan ID of a VF in preparation for "hostdev network" passthrough (this is where we set the MAC address and vlan id of the VF after detaching the host net driver and before assigning the device to the domain with PCI passthrough, i.e. "<interface type='hostdev'>", we do the setting via a netlink RTM_SETLINK message for that VF's Physical Function (PF), telling it the VF# we want to change. This sets an "administratively changed MAC" flag for that VF in the PF's driver, and from that point on (until the PF driver is reloaded, *not* merely the VF driver) that VF's MAC address can't be changed using ioctl(SIOCSIFHWADDR) - the only way to change it is via the PF with RTM_SETLINK. This means that if a VF is used for hostdev passthrough, it will have the admin flag set, and future attempts to use that VF for macvtap passthrough will fail. The solution to this problem is to check if the device being used for macvtap passthrough is actually a VF; if so, we use the netlink RTM_SETLINK message to the PF to set the VF's mac address instead of ioctl(SIOCSIFHWADDR) directly to the VF; if not, behavior does not change from previously. There are three pieces to making this work: 1) virNetDevMacVLan(Create|Delete)WithVPortProfile() now call virNetDev(Replace|Restore)NetConfig() rather than virNetDev(Replace|Restore)MacAddress() (simply passing -1 for VF# and vlanid). 2) virNetDev(Replace|Restore)NetConfig() check to see if the device is a VF. If so, they find the PF's name and VF#, allowing them to call virNetDev(Replace|Restore)VfConfig(). 3) To prevent mixups when detaching a macvtap passthrough device that had been attached while running an older version of libvirt, virNetDevRestoreVfConfig() is potentially given the preserved name of the VF, and if the proper statefile for a VF can't be found in the stateDir (${stateDir}/${pfname}_vf${vfid}), virNetDevRestoreMacAddress() is called instead (which will look in the file named ${stateDir}/${vfname}). This problem has existed in every version of libvirt that has both macvtap passthrough and interface type='hostdev'. Fortunately people seem to use one or the other though, so it hasn't caused any real world problem reports.
LibVirt : simple API for virtualization Libvirt is a C toolkit to interact with the virtualization capabilities of recent versions of Linux (and other OSes). It is free software available under the GNU Lesser General Public License. Virtualization of the Linux Operating System means the ability to run multiple instances of Operating Systems concurrently on a single hardware system where the basic resources are driven by a Linux instance. The library aim at providing long term stable C API initially for the Xen paravirtualization but should be able to integrate other virtualization mechanisms if needed. Daniel Veillard <veillard@redhat.com>