cpufreq: Add perf_freq to cpuinfo

acpi-cpufreq scales the aperf/mperf measurements by max_freq, but HWP
needs to scale by base frequency.  Settings max_freq to base_freq
"works" but the code is not obvious, and returning values to userspace
is tricky.  Add an additonal perf_freq member which is used for scaling
aperf/mperf measurements.

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

xen/arch/x86/acpi/cpufreq/cpufreq.c

@@ -316,7 +316,7 @@ unsigned int get_measured_perf(unsigned int cpu, unsigned int flag)
     else
         perf_percent = 0;
 
-    return policy->cpuinfo.max_freq * perf_percent / 100;
+    return policy->cpuinfo.perf_freq * perf_percent / 100;
 }
 
 static unsigned int cf_check get_cur_freq_on_cpu(unsigned int cpu)

xen/drivers/cpufreq/utility.c

@@ -236,6 +236,7 @@ int cpufreq_frequency_table_cpuinfo(struct cpufreq_policy *policy,
 
     policy->min = policy->cpuinfo.min_freq = min_freq;
     policy->max = policy->cpuinfo.max_freq = max_freq;
+    policy->cpuinfo.perf_freq = max_freq;
     policy->cpuinfo.second_max_freq = second_max_freq;
 
     if (policy->min == ~0)

xen/include/acpi/cpufreq/cpufreq.h

@@ -37,6 +37,9 @@ extern struct acpi_cpufreq_data *cpufreq_drv_data[NR_CPUS];
 struct cpufreq_cpuinfo {
     unsigned int        max_freq;
     unsigned int        second_max_freq;    /* P1 if Turbo Mode is on */
+    unsigned int        perf_freq; /* Scaling freq for aperf/mpref.
+                                      acpi-cpufreq uses max_freq, but HWP uses
+                                      base_freq.*/
     unsigned int        min_freq;
     unsigned int        transition_latency; /* in 10^(-9) s = nanoseconds */
 };