powerpc/kernel/sysfs: Add new config option PMU_SYSFS to enable PMU SPRs sysfs file creation

Many of the performance monitoring unit (PMU) SPRs are
exposed in the sysfs. This may not be a desirable since
"perf" API is the primary interface to program PMU and
collect counter data in the system. But that said, we
cant remove these sysfs files since we dont whether
anyone/anything is using them.

So the patch adds a new CONFIG option 'CONFIG_PMU_SYSFS'
(user selectable) to be used in sysfs file creation for
PMU SPRs. New option by default is disabled, but can be
enabled if user needs it.

Tested this patch behaviour in powernv and pseries machines.
Patch is also tested for pmac32_defconfig.
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Tested-by: Nageswara R Sastry <nasastry@in.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200214080606.26872-2-kjain@linux.ibm.com

arch/powerpc/kernel/sysfs.c

@@ -562,6 +562,7 @@ EXPORT_SYMBOL(ppc_enable_pmcs);
  * that are implemented on the current processor
  */
 
+#ifdef CONFIG_PMU_SYSFS
 #if defined(CONFIG_PPC64) || defined(CONFIG_PPC_BOOK3S_32)
 #define HAS_PPC_PMC_CLASSIC	1
 #define HAS_PPC_PMC_IBM		1
@@ -575,6 +576,7 @@ EXPORT_SYMBOL(ppc_enable_pmcs);
 #ifdef CONFIG_PPC_BOOK3S_32
 #define HAS_PPC_PMC_G4		1
 #endif
+#endif /* CONFIG_PMU_SYSFS */
 
 #if defined(CONFIG_PPC64) && defined(CONFIG_DEBUG_MISC)
 #define HAS_PPC_PA6T
@@ -812,8 +814,10 @@ static int register_cpu_online(unsigned int cpu)
 			device_create_file(s, &pmc_attrs[i]);
 
 #ifdef CONFIG_PPC64
+#ifdef	CONFIG_PMU_SYSFS
 	if (cpu_has_feature(CPU_FTR_MMCRA))
 		device_create_file(s, &dev_attr_mmcra);
+#endif /* CONFIG_PMU_SYSFS */
 
 	if (cpu_has_feature(CPU_FTR_PURR)) {
 		if (!firmware_has_feature(FW_FEATURE_LPAR))
@@ -901,8 +905,10 @@ static int unregister_cpu_online(unsigned int cpu)
 			device_remove_file(s, &pmc_attrs[i]);
 
 #ifdef CONFIG_PPC64
+#ifdef CONFIG_PMU_SYSFS
 	if (cpu_has_feature(CPU_FTR_MMCRA))
 		device_remove_file(s, &dev_attr_mmcra);
+#endif /* CONFIG_PMU_SYSFS */
 
 	if (cpu_has_feature(CPU_FTR_PURR))
 		device_remove_file(s, &dev_attr_purr);

arch/powerpc/platforms/Kconfig.cputype

@@ -425,6 +425,12 @@ config PPC_MM_SLICES
 config PPC_HAVE_PMU_SUPPORT
 	bool
 
+config PMU_SYSFS
+	bool "Create PMU SPRs sysfs file"
+	default n
+	help
+	  This option enables sysfs file creation for PMU SPRs like MMCR* and PMC*.
+
 config PPC_PERF_CTRS
 	def_bool y
 	depends on PERF_EVENTS && PPC_HAVE_PMU_SUPPORT