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s390/mm: Introduce region-third and segment table swap entries

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Introduce region-third (PUD) and segment table (PMD) swap entries, and
make hugetlbfs RSTE <-> PTE conversion code aware of them, so that they
can be used for hugetlbfs PTE_MARKER entries. Future work could also
build on this to enable THP_SWAP and THP_MIGRATION for s390.

Similar to PTE swap entries, bits 0-51 can be used to store the swap
offset, but bits 57-61 cannot be used for swap type because that overlaps
with the INVALID and TABLE TYPE bits. PMD/PUD swap entries must be invalid,
and have a correct table type so that pud_folded() check still works.

Bits 53-57 can be used for swap type, but those include the PROTECT bit.
So unlike swap PTEs, the PROTECT bit cannot be used to mark the swap entry.
Use the "Common-Segment/Region" bit 59 instead for that.

Also remove the !MACHINE_HAS_NX check in __set_huge_pte_at(). Otherwise,
that would clear the _SEGMENT_ENTRY_NOEXEC bit also for swap entries, where
it is used for encoding the swap type. The architecture only requires this
bit to be 0 for PTEs, with !MACHINE_HAS_NX, not for segment or region-third
entries. And the check is also redundant, because after __pte_to_rste()
conversion, for non-swap PTEs it would only be set if it was already set in
the PTE, which should never be the case for !MACHINE_HAS_NX.

This is a prerequisite for hugetlbfs PTE_MARKER support on s390, which
is needed to fix a regression introduced with commit 8a13897fb0
("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>
This commit is contained in:
Gerald Schaefer
2024-11-21 18:45:22 +01:00
committed by Heiko Carstens
parent 03e6db16b8
commit f934f6be76
2 changed files with 71 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

53
arch/s390/include/asm/pgtable.h
View File

@@ -286,6 +286,7 @@ static inline int is_module_addr(void *addr)
#define _REGION3_ENTRY_ORIGIN_LARGE ~0x7fffffffUL /* large page address */
#define _REGION3_ENTRY_DIRTY 0x2000 /* SW region dirty bit */
#define _REGION3_ENTRY_YOUNG 0x1000 /* SW region young bit */
#define _REGION3_ENTRY_COMM 0x0010 /* Common-Region, marks swap entry */
#define _REGION3_ENTRY_LARGE 0x0400 /* RTTE-format control, large page */
#define _REGION3_ENTRY_WRITE 0x8000 /* SW region write bit */
#define _REGION3_ENTRY_READ 0x4000 /* SW region read bit */
@@ -323,6 +324,7 @@ 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_COMM 0x0010 /* Common-Segment, marks swap entry */
#define _SEGMENT_ENTRY_LARGE 0x0400 /* STE-format control, large page */
#define _SEGMENT_ENTRY_WRITE 0x8000 /* SW segment write bit */
#define _SEGMENT_ENTRY_READ 0x4000 /* SW segment read bit */
@@ -335,6 +337,10 @@ static inline int is_module_addr(void *addr)
#define _SEGMENT_ENTRY_PRESENT 0x0001 /* SW segment present bit */
/* Common bits in region and segment table entries, for swap entries */
#define _RST_ENTRY_COMM 0x0010 /* Common-Region/Segment, marks swap entry */
#define _RST_ENTRY_INVALID 0x0020 /* invalid region/segment table entry */
#define _CRST_ENTRIES 2048 /* number of region/segment table entries */
#define _PAGE_ENTRIES 256 /* number of page table entries */
@@ -1931,6 +1937,53 @@ static inline swp_entry_t __swp_entry(unsigned long type, unsigned long offset)
#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
#define __swp_entry_to_pte(x) ((pte_t) { (x).val })
/*
* 64 bit swap entry format for REGION3 and SEGMENT table entries (RSTE)
* Bits 59 and 63 are used to indicate the swap entry. Bit 58 marks the rste
* as invalid.
* A swap entry is indicated by bit pattern (rste & 0x011) == 0x010
* | offset |Xtype |11TT|S0|
* |0000000000111111111122222222223333333333444444444455|555555|5566|66|
* |0123456789012345678901234567890123456789012345678901|234567|8901|23|
*
* Bits 0-51 store the offset.
* Bits 53-57 store the type.
* Bit 62 (S) is used for softdirty tracking.
* Bits 60-61 (TT) indicate the table type: 0x01 for REGION3 and 0x00 for SEGMENT.
* Bit 52 (X) is unused.
*/
#define __SWP_OFFSET_MASK_RSTE ((1UL << 52) - 1)
#define __SWP_OFFSET_SHIFT_RSTE 12
#define __SWP_TYPE_MASK_RSTE ((1UL << 5) - 1)
#define __SWP_TYPE_SHIFT_RSTE 6
/*
* TT bits set to 0x00 == SEGMENT. For REGION3 entries, caller must add R3
* bits 0x01. See also __set_huge_pte_at().
*/
static inline unsigned long mk_swap_rste(unsigned long type, unsigned long offset)
{
unsigned long rste;
rste = _RST_ENTRY_INVALID | _RST_ENTRY_COMM;
rste |= (offset & __SWP_OFFSET_MASK_RSTE) << __SWP_OFFSET_SHIFT_RSTE;
rste |= (type & __SWP_TYPE_MASK_RSTE) << __SWP_TYPE_SHIFT_RSTE;
return rste;
}
static inline unsigned long __swp_type_rste(swp_entry_t entry)
{
return (entry.val >> __SWP_TYPE_SHIFT_RSTE) & __SWP_TYPE_MASK_RSTE;
}
static inline unsigned long __swp_offset_rste(swp_entry_t entry)
{
return (entry.val >> __SWP_OFFSET_SHIFT_RSTE) & __SWP_OFFSET_MASK_RSTE;
}
#define __rste_to_swp_entry(rste) ((swp_entry_t) { rste })
extern int vmem_add_mapping(unsigned long start, unsigned long size);
extern void vmem_remove_mapping(unsigned long start, unsigned long size);
extern int __vmem_map_4k_page(unsigned long addr, unsigned long phys, pgprot_t prot, bool alloc);

23
arch/s390/mm/hugetlbpage.c
View File

@@ -24,6 +24,7 @@
static inline unsigned long __pte_to_rste(pte_t pte)
{
swp_entry_t arch_entry;
unsigned long rste;
/*
@@ -67,6 +68,10 @@ static inline unsigned long __pte_to_rste(pte_t pte)
#endif
rste |= move_set_bit(pte_val(pte), _PAGE_NOEXEC,
_SEGMENT_ENTRY_NOEXEC);
} else if (!pte_none(pte)) {
/* swap pte */
arch_entry = __pte_to_swp_entry(pte);
rste = mk_swap_rste(__swp_type(arch_entry), __swp_offset(arch_entry));
} else
rste = _SEGMENT_ENTRY_EMPTY;
return rste;
@@ -74,13 +79,18 @@ static inline unsigned long __pte_to_rste(pte_t pte)
static inline pte_t __rste_to_pte(unsigned long rste)
{
swp_entry_t arch_entry;
unsigned long pteval;
int present;
int present, none;
pte_t pte;
if ((rste & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3)
if ((rste & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3) {
present = pud_present(__pud(rste));
else
none = pud_none(__pud(rste));
} else {
present = pmd_present(__pmd(rste));
none = pmd_none(__pmd(rste));
}
/*
* Convert encoding pmd / pud bits pte bits
@@ -115,6 +125,11 @@ static inline pte_t __rste_to_pte(unsigned long rste)
pteval |= move_set_bit(rste, _SEGMENT_ENTRY_SOFT_DIRTY, _PAGE_SOFT_DIRTY);
#endif
pteval |= move_set_bit(rste, _SEGMENT_ENTRY_NOEXEC, _PAGE_NOEXEC);
} else if (!none) {
/* swap rste */
arch_entry = __rste_to_swp_entry(rste);
pte = mk_swap_pte(__swp_type_rste(arch_entry), __swp_offset_rste(arch_entry));
pteval = pte_val(pte);
} else
pteval = _PAGE_INVALID;
return __pte(pteval);
@@ -149,8 +164,6 @@ void __set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
unsigned long rste;
rste = __pte_to_rste(pte);
if (!MACHINE_HAS_NX)
rste &= ~_SEGMENT_ENTRY_NOEXEC;
/* Set correct table type for 2G hugepages */
if ((pte_val(*ptep) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3) {