Description of problem:
usb and redirection don't work in xen.

Version-Release number of selected component (if applicable):
qemu-system-x86-2.9.0-1.fc26.1.x86_64
xen-4.8.1-4.fc26.x86_64

How reproducible:
Every time.

Steps to Reproduce:
1. Add in xen config xl.cfg setting like "pci = [ '01:23.4' ]" or "usbctrl = [ 'version=2' ]"
2. start domU
3.

Actual results:
libxl: error: libxl_qmp.c:287:qmp_handle_error_response: received an error message from QMP server: Unsupported bus. Bus doesn't have property 'acpi-pcihp-bsel' set
libxl: error: libxl_create.c:1461:domcreate_attach_devices: unable to add usbctrl devices
libxl: error: libxl.c:1575:libxl__destroy_domid: non-existant domain 12
libxl: error: libxl.c:1534:domain_destroy_callback: unable to destroy guest with domid 12
libxl: error: libxl.c:1463:domain_destroy_cb: destruction of domain 12 failed

or

libxl: error: libxl_qmp.c:287:qmp_handle_error_response: received an error message from QMP server: Unsupported bus. Bus doesn't have property 'acpi-pcihp-bsel' set
libxl: error: libxl_pci.c:1304:libxl__add_pcidevs: libxl_device_pci_add failed: -3
libxl: error: libxl_create.c:1461:domcreate_attach_devices: unable to add pci devices
libxl: error: libxl.c:1575:libxl__destroy_domid: non-existant domain 13
libxl: error: libxl.c:1534:domain_destroy_callback: unable to destroy guest with domid 13
libxl: error: libxl.c:1463:domain_destroy_cb: destruction of domain 13 failed


Additional info:
After downgrading to qemu-system-x86-2.8.0-2.fc26.x86_64 redirections works.