xen/cpufreq: get performance policy from governor set via xenpm

Even if Xen governor is not used in amd-cppc active mode, we could
somehow deduce which performance policy (CPUFREQ_POLICY_xxx) user wants to
apply through which governor they choose, such as:
If user chooses performance governor, they want maximum performance, then
the policy shall be CPUFREQ_POLICY_PERFORMANCE
If user chooses powersave governor, they want the least power consumption,
then the policy shall be CPUFREQ_POLICY_POWERSAVE
Function cpufreq_policy_from_governor() is responsible for above transition,
and it shall be also effective when users setting new governor through xenpm.

Userspace is a forbidden choice, and if users specify such option, we shall
not only give warning message to suggest using "xenpm set-cpufreq-cppc", but
also error out.

Signed-off-by: Penny Zheng <Penny.Zheng@amd.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/drivers/acpi/pm-op.c

@@ -207,6 +207,17 @@ static int set_cpufreq_gov(struct xen_sysctl_pm_op *op)
     if ( new_policy.governor == NULL )
         return -EINVAL;
 
+    if ( processor_pminfo[op->cpuid]->init & XEN_CPPC_INIT )
+    {
+        new_policy.policy = cpufreq_policy_from_governor(new_policy.governor);
+        if ( new_policy.policy == CPUFREQ_POLICY_UNKNOWN )
+        {
+            printk("Failed to get performance policy from %s, Try \"xenpm set-cpufreq-cppc\"\n",
+                   new_policy.governor->name);
+            return -EINVAL;
+        }
+    }
+
     return __cpufreq_set_policy(old_policy, &new_policy);
 }