s390/mm: cleanup init_new_context() callback
The set of values asce_limit may be assigned with is TASK_SIZE_MAX,
_REGION1_SIZE, _REGION2_SIZE and 0 as a special case if the callback
was called from execve().
Do VM_BUG_ON() if asce_limit is something else.
Save few CPU cycles by removing unnecessary asce_limit re-assignment
in case of 3-level task and redundant PGD entry type reconstruction.
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h
index 248d51c..844396b 100644
--- a/arch/s390/include/asm/mmu_context.h
+++ b/arch/s390/include/asm/mmu_context.h
@@ -18,6 +18,8 @@
static inline int init_new_context(struct task_struct *tsk,
struct mm_struct *mm)
{
+ unsigned long asce_type, init_entry;
+
spin_lock_init(&mm->context.lock);
INIT_LIST_HEAD(&mm->context.pgtable_list);
INIT_LIST_HEAD(&mm->context.gmap_list);
@@ -35,29 +37,34 @@
mm->context.allow_gmap_hpage_1m = 0;
#endif
switch (mm->context.asce_limit) {
- case _REGION2_SIZE:
+ default:
/*
- * forked 3-level task, fall through to set new asce with new
- * mm->pgd
+ * context created by exec, the value of asce_limit can
+ * only be zero in this case
*/
- case 0:
- /* context created by exec, set asce limit to 4TB */
+ VM_BUG_ON(mm->context.asce_limit);
+ /* continue as 3-level task */
mm->context.asce_limit = _REGION2_SIZE;
- mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
- _ASCE_USER_BITS | _ASCE_TYPE_REGION3;
+ fallthrough;
+ case _REGION2_SIZE:
+ /* forked 3-level task */
+ init_entry = _REGION3_ENTRY_EMPTY;
+ asce_type = _ASCE_TYPE_REGION3;
break;
case TASK_SIZE_MAX:
- /* forked 5-level task, set new asce with new_mm->pgd */
- mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
- _ASCE_USER_BITS | _ASCE_TYPE_REGION1;
+ /* forked 5-level task */
+ init_entry = _REGION1_ENTRY_EMPTY;
+ asce_type = _ASCE_TYPE_REGION1;
break;
case _REGION1_SIZE:
- /* forked 4-level task, set new asce with new mm->pgd */
- mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
- _ASCE_USER_BITS | _ASCE_TYPE_REGION2;
+ /* forked 4-level task */
+ init_entry = _REGION2_ENTRY_EMPTY;
+ asce_type = _ASCE_TYPE_REGION2;
break;
}
- crst_table_init((unsigned long *) mm->pgd, pgd_entry_type(mm));
+ mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
+ _ASCE_USER_BITS | asce_type;
+ crst_table_init((unsigned long *) mm->pgd, init_entry);
return 0;
}
diff --git a/arch/s390/include/asm/pgalloc.h b/arch/s390/include/asm/pgalloc.h
index 5e3ff9f..74a352f 100644
--- a/arch/s390/include/asm/pgalloc.h
+++ b/arch/s390/include/asm/pgalloc.h
@@ -34,17 +34,6 @@
memset64((u64 *)crst, entry, _CRST_ENTRIES);
}
-static inline unsigned long pgd_entry_type(struct mm_struct *mm)
-{
- if (mm_pmd_folded(mm))
- return _SEGMENT_ENTRY_EMPTY;
- if (mm_pud_folded(mm))
- return _REGION3_ENTRY_EMPTY;
- if (mm_p4d_folded(mm))
- return _REGION2_ENTRY_EMPTY;
- return _REGION1_ENTRY_EMPTY;
-}
-
int crst_table_upgrade(struct mm_struct *mm, unsigned long limit);
static inline unsigned long check_asce_limit(struct mm_struct *mm, unsigned long addr,
