x86, msr: Have the _safe MSR functions return -EIO, not -EFAULT

For some reason, the _safe MSR functions returned -EFAULT, not -EIO.
However, the only user which cares about the return code as anything
other than a boolean is the MSR driver, which wants -EIO.  Change it
to -EIO across the board.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>

arch/x86/include/asm/msr.h

@@ -67,7 +67,7 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr,
 		     ".previous\n\t"
 		     _ASM_EXTABLE(2b, 3b)
 		     : [err] "=r" (*err), EAX_EDX_RET(val, low, high)
-		     : "c" (msr), [fault] "i" (-EFAULT));
+		     : "c" (msr), [fault] "i" (-EIO));
 	return EAX_EDX_VAL(val, low, high);
 }
 
@@ -90,7 +90,7 @@ notrace static inline int native_write_msr_safe(unsigned int msr,
 		     _ASM_EXTABLE(2b, 3b)
 		     : [err] "=a" (err)
 		     : "c" (msr), "0" (low), "d" (high),
-		       [fault] "i" (-EFAULT)
+		       [fault] "i" (-EIO)
 		     : "memory");
 	return err;
 }

arch/x86/kernel/msr.c

@@ -80,11 +80,8 @@ static ssize_t msr_read(struct file *file, char __user *buf,
 
 	for (; count; count -= 8) {
 		err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
-		if (err) {
-			if (err == -EFAULT) /* Fix idiotic error code */
-				err = -EIO;
+		if (err)
 			break;
-		}
 		if (copy_to_user(tmp, &data, 8)) {
 			err = -EFAULT;
 			break;
@@ -115,11 +112,8 @@ static ssize_t msr_write(struct file *file, const char __user *buf,
 			break;
 		}
 		err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);
-		if (err) {
-			if (err == -EFAULT) /* Fix idiotic error code */
-				err = -EIO;
+		if (err)
 			break;
-		}
 		tmp += 2;
 		bytes += 8;
 	}

arch/x86/xen/enlighten.c

@@ -713,7 +713,7 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
 	set:
 		base = ((u64)high << 32) | low;
 		if (HYPERVISOR_set_segment_base(which, base) != 0)
-			ret = -EFAULT;
+			ret = -EIO;
 		break;
 #endif