[Qemu-devel] [PULL 13/29] s390x/mmu: Add support for read-only regions

[Christian Borntraeger]

From: Thomas Huth <address@hidden>

If the "DAT-protection" bit is set in the region table entry and EDAT is
enabled, only read accesses are allowed in the corresponding memory area.

Signed-off-by: Thomas Huth <address@hidden>
Signed-off-by: Jens Freimann <address@hidden>
Reviewed-by: David Hildenbrand <address@hidden>
Reviewed-by: Cornelia Huck <address@hidden>
Signed-off-by: Christian Borntraeger <address@hidden>
---
 target-s390x/cpu.h        | 1 +
 target-s390x/mmu_helper.c | 7 ++++---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h
index c0016b6..08cdb15 100644
--- a/target-s390x/cpu.h
+++ b/target-s390x/cpu.h
@@ -837,6 +837,7 @@ struct sysib_322 {
 #define _ASCE_TABLE_LENGTH      0x03      /* region table length              
*/
 
 #define _REGION_ENTRY_ORIGIN    ~0xfffULL /* region/segment table origin      
*/
+#define _REGION_ENTRY_RO        0x200     /* region/segment protection bit    
*/
 #define _REGION_ENTRY_TF        0xc0      /* region/segment table offset      
*/
 #define _REGION_ENTRY_INV       0x20      /* invalid region table entry       
*/
 #define _REGION_ENTRY_TYPE_MASK 0x0c      /* region/segment table type mask   
*/
diff --git a/target-s390x/mmu_helper.c b/target-s390x/mmu_helper.c
index 0c53ae9..702e8b8 100644
--- a/target-s390x/mmu_helper.c
+++ b/target-s390x/mmu_helper.c
@@ -188,9 +188,6 @@ static int mmu_translate_region(CPUS390XState *env, 
target_ulong vaddr,
         return -1;
     }
 
-    /* XXX region protection flags */
-    /* *flags &= ~PAGE_WRITE */
-
     if (level == _ASCE_TYPE_SEGMENT) {
         return mmu_translate_segment(env, vaddr, asc, new_entry, raddr, flags,
                                      rw, exc);
@@ -205,6 +202,10 @@ static int mmu_translate_region(CPUS390XState *env, 
target_ulong vaddr,
         return -1;
     }
 
+    if ((env->cregs[0] & CR0_EDAT) && (new_entry & _REGION_ENTRY_RO)) {
+        *flags &= ~PAGE_WRITE;
+    }
+
     /* yet another region */
     return mmu_translate_region(env, vaddr, asc, new_entry, level - 4,
                                 raddr, flags, rw, exc);
-- 
1.9.3