x86: msr: propagate errors from smp_call_function_single()

Propagate error (-ENXIO) from smp_call_function_single().  These
errors can happen when a CPU is unplugged while the MSR driver is
open.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/arch/x86/lib/msr-on-cpu.c b/arch/x86/lib/msr-on-cpu.c
index d5a2b39..01b868b 100644
--- a/arch/x86/lib/msr-on-cpu.c
+++ b/arch/x86/lib/msr-on-cpu.c
@@ -30,10 +30,11 @@
 
 	rv.msr_no = msr_no;
 	if (safe) {
-		smp_call_function_single(cpu, __rdmsr_safe_on_cpu, &rv, 1);
-		err = rv.err;
+		err = smp_call_function_single(cpu, __rdmsr_safe_on_cpu,
+					       &rv, 1);
+		err = err ? err : rv.err;
 	} else {
-		smp_call_function_single(cpu, __rdmsr_on_cpu, &rv, 1);
+		err = smp_call_function_single(cpu, __rdmsr_on_cpu, &rv, 1);
 	}
 	*l = rv.l;
 	*h = rv.h;
@@ -64,23 +65,24 @@
 	rv.l = l;
 	rv.h = h;
 	if (safe) {
-		smp_call_function_single(cpu, __wrmsr_safe_on_cpu, &rv, 1);
-		err = rv.err;
+		err = smp_call_function_single(cpu, __wrmsr_safe_on_cpu,
+					       &rv, 1);
+		err = err ? err : rv.err;
 	} else {
-		smp_call_function_single(cpu, __wrmsr_on_cpu, &rv, 1);
+		err = smp_call_function_single(cpu, __wrmsr_on_cpu, &rv, 1);
 	}
 
 	return err;
 }
 
-void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
+int wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
 {
-	_wrmsr_on_cpu(cpu, msr_no, l, h, 0);
+	return _wrmsr_on_cpu(cpu, msr_no, l, h, 0);
 }
 
-void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
+int rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
 {
-	_rdmsr_on_cpu(cpu, msr_no, l, h, 0);
+	return _rdmsr_on_cpu(cpu, msr_no, l, h, 0);
 }
 
 /* These "safe" variants are slower and should be used when the target MSR