pmstat: Limit hypercalls under HWP

When HWP is active, the cpufreq P-state information is not updated.  In
that case, return -EOPNOTSUPP instead of bogus, incomplete info.

Similarly, set_cpufreq_para() is not applicable when HWP is active.
Many of the options already checked the governor and were inaccessible,
but SCALING_MIN/MAX_FREQ was still accessible (though it would do
nothing).  Add an ealier HWP check to handle all cases.

Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/drivers/acpi/pmstat.c

@@ -66,6 +66,8 @@ int do_get_pm_info(struct xen_sysctl_get_pmstat *op)
             return -ENODEV;
         if ( !cpufreq_driver.init )
             return -ENODEV;
+        if ( hwp_active() )
+            return -EOPNOTSUPP;
         if ( !pmpt || !(pmpt->perf.init & XEN_PX_INIT) )
             return -EINVAL;
         break;
@@ -330,6 +332,9 @@ static int set_cpufreq_para(struct xen_sysctl_pm_op *op)
     if ( !policy || !policy->governor )
         return -EINVAL;
 
+    if ( hwp_active() )
+        return -EOPNOTSUPP;
+
     switch(op->u.set_para.ctrl_type)
     {
     case SCALING_MAX_FREQ: