powerpc: Mark some variables in the page fault path __read_mostly

Using perf to trace L1 dcache misses and dumping data addresses I found a few
variables taking a lot of misses. Since they are almost never written, they
should go into the __read_mostly section.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/traps.c

@@ -60,13 +60,13 @@
 #endif
 
 #if defined(CONFIG_DEBUGGER) || defined(CONFIG_KEXEC)
-int (*__debugger)(struct pt_regs *regs);
-int (*__debugger_ipi)(struct pt_regs *regs);
-int (*__debugger_bpt)(struct pt_regs *regs);
-int (*__debugger_sstep)(struct pt_regs *regs);
-int (*__debugger_iabr_match)(struct pt_regs *regs);
-int (*__debugger_dabr_match)(struct pt_regs *regs);
-int (*__debugger_fault_handler)(struct pt_regs *regs);
+int (*__debugger)(struct pt_regs *regs) __read_mostly;
+int (*__debugger_ipi)(struct pt_regs *regs) __read_mostly;
+int (*__debugger_bpt)(struct pt_regs *regs) __read_mostly;
+int (*__debugger_sstep)(struct pt_regs *regs) __read_mostly;
+int (*__debugger_iabr_match)(struct pt_regs *regs) __read_mostly;
+int (*__debugger_dabr_match)(struct pt_regs *regs) __read_mostly;
+int (*__debugger_fault_handler)(struct pt_regs *regs) __read_mostly;
 
 EXPORT_SYMBOL(__debugger);
 EXPORT_SYMBOL(__debugger_ipi);

arch/powerpc/xmon/xmon.c

@@ -61,7 +61,7 @@ static int xmon_owner;
 static int xmon_gate;
 #endif /* CONFIG_SMP */
 
-static unsigned long in_xmon = 0;
+static unsigned long in_xmon __read_mostly = 0;
 
 static unsigned long adrs;
 static int size = 1;