Re: [libvirt] [PATCH] qemu: Use legacy USB on ppc64

Commit 8156493d8db9 changed libvirt so that '-device pci-ohci' would be used instead of '-usb' on ppc64 when no specific USB controller model had been specified in the guest configuration.   While the device that ends up being presented by the guest is exactly the same, '-usb' causes it to be assigned to PCI address 00:00.0 while '-device pci-ohci', being subject to the regular PCI address assignment logic, will be at a different address.   This PCI address mismatch breaks migration of existing guests to new libvirt versions.   Luckily, when QEMU has switched its default '-usb' controller from pci-ohci to nec-usb-xhci (QEMU commit 57040d451315), it has done so without affecting older machine types, which means we can keep using '-usb' without risking guest ABI breakage.   Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1357468 ---   src/qemu/qemu_command.c                                       | 8 +++++---   tests/qemuxml2argvdata/qemuxml2argv-ppc64-usb-controller.args | 2 +-   tests/qemuxml2argvdata/qemuxml2argv-pseries-usb-default.args  | 2 +-   3 files changed, 7 insertions(+), 5 deletions(-)