xen/dom0: set wallclock time in Xen

static int xen_set_wallclock(unsigned long now)

{

	struct xen_platform_op op;

	int rc;

	/* do nothing for domU */

	if (!xen_initial_domain())

		return -1;

	op.cmd = XENPF_settime;

	op.u.settime.secs = now;

	op.u.settime.nsecs = 0;

	op.u.settime.system_time = xen_clocksource_read();

	rc = HYPERVISOR_dom0_op(&op);

	WARN(rc != 0, "XENPF_settime failed: now=%ld\n", now);

	return rc;

}

static struct clocksource xen_clocksource __read_mostly = {