[S390] hibernate: make sure pfn_is_nosave handles lowcore pages

pfn_is_nosave doesn't return the correct value for the second lowcore
page if lowcore protection is enabled. Make sure it always returns
the correct value.

While at it simplify the whole thing.
NSS special handling is done by the tprot check like it already works
for DCSS as well. So remove the extra code for NSS.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/lowcore.h

@@ -195,6 +195,8 @@ union save_area {
 #define LC_ORDER 1
 #endif
 
+#define LC_PAGES (1UL << LC_ORDER)
+
 struct _lowcore
 {
 #ifndef __s390x__

arch/s390/kernel/suspend.c

@@ -6,36 +6,26 @@
  * Author(s): Hans-Joachim Picht <hans@linux.vnet.ibm.com>
  */
 
-#include <linux/suspend.h>
-#include <linux/reboot.h>
 #include <linux/pfn.h>
-#include <linux/mm.h>
-#include <asm/sections.h>
 #include <asm/system.h>
-#include <asm/ipl.h>
 
 /*
  * References to section boundaries
  */
 extern const void __nosave_begin, __nosave_end;
 
-/*
- *  check if given pfn is in the 'nosave' or in the read only NSS section
- */
 int pfn_is_nosave(unsigned long pfn)
 {
-	unsigned long nosave_begin_pfn = __pa(&__nosave_begin) >> PAGE_SHIFT;
-	unsigned long nosave_end_pfn = PAGE_ALIGN(__pa(&__nosave_end))
-					>> PAGE_SHIFT;
-	unsigned long eshared_pfn = PFN_DOWN(__pa(&_eshared)) - 1;
-	unsigned long stext_pfn = PFN_DOWN(__pa(&_stext));
+	unsigned long nosave_begin_pfn = PFN_DOWN(__pa(&__nosave_begin));
+	unsigned long nosave_end_pfn = PFN_DOWN(__pa(&__nosave_end));
 
+	/* Always save lowcore pages (LC protection might be enabled). */
+	if (pfn <= LC_PAGES)
+		return 0;
 	if (pfn >= nosave_begin_pfn && pfn < nosave_end_pfn)
 		return 1;
-	if (pfn >= stext_pfn && pfn <= eshared_pfn) {
-		if (ipl_info.type == IPL_TYPE_NSS)
-			return 1;
-	} else if ((tprot(pfn * PAGE_SIZE) && pfn > 0))
+	/* Skip memory holes and read-only pages (NSS, DCSS, ...). */
+	if (tprot(PFN_PHYS(pfn)))
 		return 1;
 	return 0;
 }