s390/pci: do not read data after failed load

If a pci load instruction fails the content of the register where the
data is stored is possibly unchanged. Fix the inline assembly wrapper
__pcilg to not return stale data. Additionally fix the callers of this
function who access uninitialized variables.
Reviewed-by: NGerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: NSebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/pci_io.h

@@ -92,6 +92,9 @@ static inline int zpci_read_single(u64 req, u64 *dst, u64 offset, u8 len)
 	int cc;
 
 	cc = s390pci_load(&data, req, offset);
+	if (cc)
+		goto out;
+
 	switch (len) {
 	case 1:
 		*((u8 *) dst) = (u8) data;
@@ -106,6 +109,7 @@ static inline int zpci_read_single(u64 req, u64 *dst, u64 offset, u8 len)
 		*((u64 *) dst) = (u64) data;
 		break;
 	}
+out:
 	return cc;
 }
 

arch/s390/pci/pci.c

@@ -281,11 +281,11 @@ static int zpci_cfg_load(struct zpci_dev *zdev, int offset, u32 *val, u8 len)
 	int rc;
 
 	rc = s390pci_load(&data, req, offset);
-	data = data << ((8 - len) * 8);
-	data = le64_to_cpu(data);
-	if (!rc)
+	if (!rc) {
+		data = data << ((8 - len) * 8);
+		data = le64_to_cpu(data);
 		*val = (u32) data;
-	else
+	} else
 		*val = 0xffffffff;
 	return rc;
 }

arch/s390/pci/pci_insn.c

@@ -103,7 +103,9 @@ static inline int __pcilg(u64 *data, u64 req, u64 offset, u8 *status)
 		:  "d" (__offset)
 		: "cc");
 	*status = __req >> 24 & 0xff;
-	*data = __data;
+	if (!cc)
+		*data = __data;
+
 	return cc;
 }