s390/diag: handle diag 204 subcode 4 address correctly

Diagnose 204 subcode 4 requires a real (physical) address, but a
virtual address is passed to the inline assembly.

Convert the address to a physical address for only this specific case.

Acked-by: Alexander Gordeev <[e-mail]>
Reviewed-by: Christian Borntraeger <[e-mail]>
Signed-off-by: Heiko Carstens <[e-mail]>

arch/s390/include/asm/diag.h

···
 	DIAG204_SUBC_STIB7 = 7
 };
 
+#define DIAG204_SUBCODE_MASK 0xffff
+
 /* The two available diag 204 data formats */
 enum diag204_format {
 	DIAG204_INFO_SIMPLE = 0,

arch/s390/kernel/diag.c

···
 int diag204(unsigned long subcode, unsigned long size, void *addr)
 {
 	diag_stat_inc(DIAG_STAT_X204);
+	if ((subcode & DIAG204_SUBCODE_MASK) == DIAG204_SUBC_STIB4)
+		addr = (void *)__pa(addr);
 	size = __diag204(&subcode, size, addr);
 	if (subcode)
 		return -1;