powerpc: Return the new MSR from msr_check_and_set()

msr_check_and_set() always performs a mfmsr() to determine if it needs
to perform an mtmsr(), as mfmsr() can be a costly operation
msr_check_and_set() could return the MSR now on the CPU to avoid
callers of msr_check_and_set having to make their own mfmsr() call.

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/reg.h

@@ -1250,7 +1250,7 @@ static inline void mtmsr_isync(unsigned long val)
 				     : "memory")
 #endif
 
-extern void msr_check_and_set(unsigned long bits);
+extern unsigned long msr_check_and_set(unsigned long bits);
 extern bool strict_msr_control;
 extern void __msr_check_and_clear(unsigned long bits);
 static inline void msr_check_and_clear(unsigned long bits)

arch/powerpc/kernel/process.c

@@ -111,7 +111,7 @@ static int __init enable_strict_msr_control(char *str)
 }
 early_param("ppc_strict_facility_enable", enable_strict_msr_control);
 
-void msr_check_and_set(unsigned long bits)
+unsigned long msr_check_and_set(unsigned long bits)
 {
 	unsigned long oldmsr = mfmsr();
 	unsigned long newmsr;
@@ -125,6 +125,8 @@ void msr_check_and_set(unsigned long bits)
 
 	if (oldmsr != newmsr)
 		mtmsr_isync(newmsr);
+
+	return newmsr;
 }
 
 void __msr_check_and_clear(unsigned long bits)