xen/sysctl: introduce CONFIG_PM_STATS

We introduce a new Kconfig CONFIG_PM_STATS for wrapping all operations
regarding performance management statistics.
The major codes reside in xen/drivers/acpi/pmstat.c, including the
pm-statistic-related sysctl op: do_get_pm_info().
CONFIG_PM_STATS also shall depend on CONFIG_SYSCTL

We shall also provide "# CONFIG_PM_STATS is not set" in preset configs for
PV shim on x86.

Signed-off-by: Penny Zheng <Penny.Zheng@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/acpi/cpu_idle.c

@@ -1489,6 +1489,7 @@ static void amd_cpuidle_init(struct acpi_processor_power *power)
         vendor_override = -1;
 }
 
+#ifdef CONFIG_PM_STATS
 uint32_t pmstat_get_cx_nr(unsigned int cpu)
 {
     return processor_powers[cpu] ? processor_powers[cpu]->count : 0;
@@ -1608,6 +1609,7 @@ int pmstat_reset_cx_stat(unsigned int cpu)
 {
     return 0;
 }
+#endif /* CONFIG_PM_STATS */
 
 void cpuidle_disable_deep_cstate(void)
 {

xen/arch/x86/configs/pvshim_defconfig

@@ -27,3 +27,4 @@ CONFIG_EXPERT=y
 # CONFIG_DEBUG is not set
 # CONFIG_GDBSX is not set
 # CONFIG_PM_OP is not set
+# CONFIG_PM_STATS is not set

xen/common/Kconfig

@@ -628,4 +628,12 @@ config PM_OP
 	  This option shall enable userspace performance management control
 	  to do power/performance analyzing and tuning.
 
+config PM_STATS
+	bool "Enable Performance Management Statistics"
+	depends on ACPI && HAS_CPUFREQ && SYSCTL
+	default y
+	help
+	  Enable collection of performance management statistics to aid in
+	  analyzing and tuning power/performance characteristics of the system
+
 endmenu

xen/common/sysctl.c

@@ -170,7 +170,7 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xen_sysctl_t) u_sysctl)
         op->u.availheap.avail_bytes <<= PAGE_SHIFT;
         break;
 
-#if defined (CONFIG_ACPI) && defined (CONFIG_HAS_CPUFREQ)
+#ifdef CONFIG_PM_STATS
     case XEN_SYSCTL_get_pmstat:
         ret = do_get_pm_info(&op->u.get_pmstat);
         break;

xen/drivers/acpi/Makefile

@@ -5,7 +5,7 @@ obj-$(CONFIG_X86) += apei/
 obj-bin-y += tables.init.o
 obj-$(CONFIG_ACPI_NUMA) += numa.o
 obj-y += osl.o
-obj-$(CONFIG_HAS_CPUFREQ) += pmstat.o
+obj-$(CONFIG_PM_STATS) += pmstat.o
 obj-$(CONFIG_PM_OP) += pm-op.o
 
 obj-$(CONFIG_X86) += hwregs.o

xen/include/acpi/cpufreq/processor_perf.h

@@ -9,9 +9,19 @@
 
 unsigned int powernow_register_driver(void);
 unsigned int get_measured_perf(unsigned int cpu, unsigned int flag);
+#ifdef CONFIG_PM_STATS
 void cpufreq_statistic_update(unsigned int cpu, uint8_t from, uint8_t to);
 int  cpufreq_statistic_init(unsigned int cpu);
 void cpufreq_statistic_exit(unsigned int cpu);
+#else
+static inline void cpufreq_statistic_update(unsigned int cpu, uint8_t from,
+                                            uint8_t to) {}
+static inline int cpufreq_statistic_init(unsigned int cpu)
+{
+    return 0;
+}
+static inline void cpufreq_statistic_exit(unsigned int cpu) {}
+#endif /* CONFIG_PM_STATS */
 
 int  cpufreq_limit_change(unsigned int cpu);