s390/ipl: fix physical-virtual confusion for diag308

Diag 308 subcodes expect a physical address as their parameter.

This currently is not a bug, but in the future physical and virtual
addresses might differ.

Fix the confusion by doing a virtual-to-physical conversion in the
exported diag308() and leave the assembly wrapper __diag308() alone.

Note that several callers pass NULL as addr, so check for the case when
NULL is passed and pass 0 to hardware since virt_to_phys(0) might be
nonzero.

Suggested-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/kernel/ipl.c

@@ -176,11 +176,11 @@ static bool reipl_fcp_clear;
 static bool reipl_ccw_clear;
 static bool reipl_eckd_clear;
 
-static inline int __diag308(unsigned long subcode, void *addr)
+static inline int __diag308(unsigned long subcode, unsigned long addr)
 {
 	union register_pair r1;
 
-	r1.even = (unsigned long) addr;
+	r1.even = addr;
 	r1.odd	= 0;
 	asm volatile(
 		"	diag	%[r1],%[subcode],0x308\n"
@@ -195,7 +195,7 @@ static inline int __diag308(unsigned long subcode, void *addr)
 int diag308(unsigned long subcode, void *addr)
 {
 	diag_stat_inc(DIAG_STAT_X308);
-	return __diag308(subcode, addr);
+	return __diag308(subcode, addr ? virt_to_phys(addr) : 0);
 }
 EXPORT_SYMBOL_GPL(diag308);