Commit 1058c163 authored by Alexander Gordeev's avatar Alexander Gordeev Committed by Vasily Gorbik
Browse files

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: default avatarAlexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent f7555608

arch/s390/include/asm/mmu_context.h

+21 −14
Original line number Diff line number Diff line
@@ -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 @@ static inline int init_new_context(struct task_struct *tsk, 
	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;

}

arch/s390/include/asm/pgalloc.h

+0 −11
Original line number Diff line number Diff line
@@ -34,17 +34,6 @@ static inline void crst_table_init(unsigned long *crst, unsigned long entry) 
	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,

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