These changes are applied only if the hostdev has a parent net device
(i.e. if it was defined as "<interface type='hostdev'>" rather than
just "<hostdev>").  If the parent netdevice has virtual port
information, the original virtualport associate functions are called
(these set and restore both mac and port profile on an
interface). Otherwise, only mac address is set on the device.

Note that This is only supported for SR-IOV Virtual Functions (not for
standard PCI or USB netdevs), and virtualport association is only
supported for 802.1Qbh. For all other types of cards and types of
virtualport, a "Config Unsupported" error is returned and the
operation fails.
Signed-off-by: NRoopa Prabhu <roprabhu@cisco.com>

In order to avoid situation where a USB device is
in use by two domains, we must keep a list of already
attached devices like we do for PCI.

When failing on starting a domain, it tries to reattach all the PCI
devices defined in the domain conf, regardless of whether the devices
are still used by other domain. This will cause the devices to be deleted
from the list qemu_driver->activePciHostdevs, thus the devices will be
thought as usable even if it's not true. And following commands
nodedev-{reattach,reset} will be successful.

How to reproduce:
  1) Define two domains with same PCI device defined in the confs.
  2) # virsh start domain1
  3) # virsh start domain2
  4) # virsh nodedev-reattach $pci_device

You will see the device will be reattached to host successfully.
As pciDeviceReattach just check if the device is still used by
other domain via checking if the device is in list driver->activePciHostdevs,
however, the device is deleted from the list by step 2).

This patch is to prohibit the bug by:
  1) Prohibit a domain starting or device attachment right at
     preparation period (qemuPrepareHostdevPCIDevices) if the
     device is in list driver->activePciHostdevs, which means
     it's used by other domain.

  2) Introduces a new field for struct _pciDevice, (const char *used_by),
     it will be set as the domain name at preparation period,
     (qemuPrepareHostdevPCIDevices). Thus we can prohibit deleting
     the device from driver->activePciHostdevs if it's still used by
     other domain when stopping the domain process.

* src/pci.h (define two internal functions, pciDeviceSetUsedBy and
    pciDevceGetUsedBy)
* src/pci.c (new field "const char *used_by" for struct _pciDevice,
    implementations for the two new functions)
* src/libvirt_private.syms (Add the two new internal functions)
* src/qemu_hostdev.h (Modify the definition of functions
    qemuPrepareHostdevPCIDevices, and qemuDomainReAttachHostdevDevices)
* src/qemu_hostdev.c (Prohibit preparation and don't delete the
    device from activePciHostdevs list if it's still used by other domain)
* src/qemu_hotplug.c (Update function usage, as the definitions are
    changed)
Signed-off-by: NEric Blake <eblake@redhat.com>

The QEMU driver file is far too large. Move all the hostdev
helper code out into a separate file. No functional change.

* src/qemu/qemu_hostdev.c, src/qemu/qemu_hostdev.h,
  src/Makefile.am: Add hostdev helper file
* src/qemu/qemu_driver.c: Delete hostdev code