powerpc: Keep track of emulated instructions

If CONFIG_PPC_EMULATED_STATS is enabled, make available counters for the
various classes of emulated instructions under
/sys/kernel/debug/powerpc/emulated_instructions/ (assumed debugfs is mounted on
/sys/kernel/debug).  Optionally (controlled by
/sys/kernel/debug/powerpc/emulated_instructions/do_warn), rate-limited warnings
can be printed to the console when instructions are emulated.

Signed-off-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
index a1098e2..d79a902 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -41,6 +41,19 @@
 	  This option will add a small amount of overhead to all hypervisor
 	  calls.
 
+config PPC_EMULATED_STATS
+	bool "Emulated instructions tracking"
+	depends on DEBUG_FS
+	help
+	  Adds code to keep track of the number of instructions that are
+	  emulated by the in-kernel emulator. Counters for the various classes
+	  of emulated instructions are available under
+	  powerpc/emulated_instructions/ in the root of the debugfs file
+	  system. Optionally (controlled by
+	  powerpc/emulated_instructions/do_warn in debugfs), rate-limited
+	  warnings can be printed to the console when instructions are
+	  emulated.
+
 config CODE_PATCHING_SELFTEST
 	bool "Run self-tests of the code-patching code."
 	depends on DEBUG_KERNEL