s390/mm: Rearrange region-third and segment table entry SW bits

JIRA: https://issues.redhat.com/browse/RHEL-74362
Tested: by me

commit ae1b9fb
Author: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Date:   Thu Nov 21 18:45:20 2024 +0100

    s390/mm: Rearrange region-third and segment table entry SW bits

    Rearrange region-third and segment table entry SW bits, in order to
    make room for future encoding of region/segment table swap entries.

    Also adjust _SEGMENT_ENTRY_GMAP_UC and _SEGMENT_ENTRY_GMAP_IN bits in
    gmap code. Those should only apply for gmap PMDs, and not really depend
    on or conflict with host PMD bits, but for consistency also adjust them:
    - _SEGMENT_ENTRY_GMAP_UC "dirty (migration)" was using the same bit as
      _SEGMENT_ENTRY_SOFT_DIRTY in the host PMD -> make it use the new
      SOFT_DIRTY bit 63 (0x0002)
    - _SEGMENT_ENTRY_GMAP_IN "invalidation notify bit" was using 0x8000,
      which was an unused bit in the host PMD, that is now used for
      _SEGMENT_ENTRY_WRITE -> make it use bit 52 (0x0800) instead, which is
      still unused in the host PMD

    This is a prerequisite for hugetlbfs PTE_MARKER support on s390, which
    is needed to fix a regression introduced with commit 8a13897
    ("mm: userfaultfd: support UFFDIO_POISON for hugetlbfs"). That commit
    depends on the availability of swap entries for hugetlbfs, which were
    not available for s390 so far.

    Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
    Signed-off-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
    Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Signed-off-by: Aristeu Rozanski <arozansk@redhat.com>

Author: aristeu

arch/s390/include/asm/gmap.h

@@ -17,8 +17,8 @@
 #define GMAP_NOTIFY_MPROT	0x1
 
 /* Status bits only for huge segment entries */
-#define _SEGMENT_ENTRY_GMAP_IN		0x8000	/* invalidation notify bit */
-#define _SEGMENT_ENTRY_GMAP_UC		0x4000	/* dirty (migration) */
+#define _SEGMENT_ENTRY_GMAP_IN		0x0800	/* invalidation notify bit */
+#define _SEGMENT_ENTRY_GMAP_UC		0x0002	/* dirty (migration) */
 
 /**
  * struct gmap_struct - guest address space

arch/s390/include/asm/pgtable.h

@@ -266,11 +266,11 @@ static inline int is_module_addr(void *addr)
 #define _REGION3_ENTRY_DIRTY	0x2000	/* SW region dirty bit */
 #define _REGION3_ENTRY_YOUNG	0x1000	/* SW region young bit */
 #define _REGION3_ENTRY_LARGE	0x0400	/* RTTE-format control, large page  */
-#define _REGION3_ENTRY_WRITE	0x0002	/* SW region write bit */
-#define _REGION3_ENTRY_READ	0x0001	/* SW region read bit */
+#define _REGION3_ENTRY_WRITE	0x8000	/* SW region write bit */
+#define _REGION3_ENTRY_READ	0x4000	/* SW region read bit */
 
 #ifdef CONFIG_MEM_SOFT_DIRTY
-#define _REGION3_ENTRY_SOFT_DIRTY 0x4000 /* SW region soft dirty bit */
+#define _REGION3_ENTRY_SOFT_DIRTY 0x0002 /* SW region soft dirty bit */
 #else
 #define _REGION3_ENTRY_SOFT_DIRTY 0x0000 /* SW region soft dirty bit */
 #endif
@@ -293,12 +293,13 @@ static inline int is_module_addr(void *addr)
 
 #define _SEGMENT_ENTRY_DIRTY	0x2000	/* SW segment dirty bit */
 #define _SEGMENT_ENTRY_YOUNG	0x1000	/* SW segment young bit */
+
 #define _SEGMENT_ENTRY_LARGE	0x0400	/* STE-format control, large page */
-#define _SEGMENT_ENTRY_WRITE	0x0002	/* SW segment write bit */
-#define _SEGMENT_ENTRY_READ	0x0001	/* SW segment read bit */
+#define _SEGMENT_ENTRY_WRITE	0x8000	/* SW segment write bit */
+#define _SEGMENT_ENTRY_READ	0x4000	/* SW segment read bit */
 
 #ifdef CONFIG_MEM_SOFT_DIRTY
-#define _SEGMENT_ENTRY_SOFT_DIRTY 0x4000 /* SW segment soft dirty bit */
+#define _SEGMENT_ENTRY_SOFT_DIRTY 0x0002 /* SW segment soft dirty bit */
 #else
 #define _SEGMENT_ENTRY_SOFT_DIRTY 0x0000 /* SW segment soft dirty bit */
 #endif