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linux/arch/s390/mm/hugetlbpage.c
Gerald Schaefer bc29b7ac1d s390/mm: clean up pte/pmd encoding 
The hugetlbfs pte<->pmd conversion functions currently assume that the pmd
bit layout is consistent with the pte layout, which is not really true.

The SW read and write bits are encoded as the sequence "wr" in a pte, but
in a pmd it is "rw". The hugetlbfs conversion assumes that the sequence
is identical in both cases, which results in swapped read and write bits
in the pmd. In practice this is not a problem, because those pmd bits are
only relevant for THP pmds and not for hugetlbfs pmds. The hugetlbfs code
works on (fake) ptes, and the converted pte bits are correct.

There is another variation in pte/pmd encoding which affects dirty
prot-none ptes/pmds. In this case, a pmd has both its HW read-only and
invalid bit set, while it is only the invalid bit for a pte. This also has
no effect in practice, but it should better be consistent.

This patch fixes both inconsistencies by changing the SW read/write bit
layout for pmds as well as the PAGE_NONE encoding for ptes. It also makes
the hugetlbfs conversion functions more robust by introducing a
move_set_bit() macro that uses the pte/pmd bit #defines instead of
constant shifts.

Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2016-07-31 05:27:57 -04:00

227 lines
6.5 KiB
C
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/*
* IBM System z Huge TLB Page Support for Kernel.
*
* Copyright IBM Corp. 2007,2016
* Author(s): Gerald Schaefer <gerald.schaefer@de.ibm.com>
*/
#define KMSG_COMPONENT "hugetlb"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
#include <linux/mm.h>
#include <linux/hugetlb.h>
/*
* If the bit selected by single-bit bitmask "a" is set within "x", move
* it to the position indicated by single-bit bitmask "b".
*/
#define move_set_bit(x, a, b) (((x) & (a)) >> ilog2(a) << ilog2(b))
static inline unsigned long __pte_to_rste(pte_t pte)
{
unsigned long rste;
/*
* Convert encoding pte bits pmd / pud bits
* lIR.uswrdy.p dy..R...I...wr
* empty 010.000000.0 -> 00..0...1...00
* prot-none, clean, old 111.000000.1 -> 00..1...1...00
* prot-none, clean, young 111.000001.1 -> 01..1...1...00
* prot-none, dirty, old 111.000010.1 -> 10..1...1...00
* prot-none, dirty, young 111.000011.1 -> 11..1...1...00
* read-only, clean, old 111.000100.1 -> 00..1...1...01
* read-only, clean, young 101.000101.1 -> 01..1...0...01
* read-only, dirty, old 111.000110.1 -> 10..1...1...01
* read-only, dirty, young 101.000111.1 -> 11..1...0...01
* read-write, clean, old 111.001100.1 -> 00..1...1...11
* read-write, clean, young 101.001101.1 -> 01..1...0...11
* read-write, dirty, old 110.001110.1 -> 10..0...1...11
* read-write, dirty, young 100.001111.1 -> 11..0...0...11
* HW-bits: R read-only, I invalid
* SW-bits: p present, y young, d dirty, r read, w write, s special,
* u unused, l large
*/
if (pte_present(pte)) {
rste = pte_val(pte) & PAGE_MASK;
rste |= move_set_bit(pte_val(pte), _PAGE_READ,
_SEGMENT_ENTRY_READ);
rste |= move_set_bit(pte_val(pte), _PAGE_WRITE,
_SEGMENT_ENTRY_WRITE);
rste |= move_set_bit(pte_val(pte), _PAGE_INVALID,
_SEGMENT_ENTRY_INVALID);
rste |= move_set_bit(pte_val(pte), _PAGE_PROTECT,
_SEGMENT_ENTRY_PROTECT);
rste |= move_set_bit(pte_val(pte), _PAGE_DIRTY,
_SEGMENT_ENTRY_DIRTY);
rste |= move_set_bit(pte_val(pte), _PAGE_YOUNG,
_SEGMENT_ENTRY_YOUNG);
#ifdef CONFIG_MEM_SOFT_DIRTY
rste |= move_set_bit(pte_val(pte), _PAGE_SOFT_DIRTY,
_SEGMENT_ENTRY_SOFT_DIRTY);
#endif
} else
rste = _SEGMENT_ENTRY_INVALID;
return rste;
}
static inline pte_t __rste_to_pte(unsigned long rste)
{
int present;
pte_t pte;
if ((rste & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3)
present = pud_present(__pud(rste));
else
present = pmd_present(__pmd(rste));
/*
* Convert encoding pmd / pud bits pte bits
* dy..R...I...wr lIR.uswrdy.p
* empty 00..0...1...00 -> 010.000000.0
* prot-none, clean, old 00..1...1...00 -> 111.000000.1
* prot-none, clean, young 01..1...1...00 -> 111.000001.1
* prot-none, dirty, old 10..1...1...00 -> 111.000010.1
* prot-none, dirty, young 11..1...1...00 -> 111.000011.1
* read-only, clean, old 00..1...1...01 -> 111.000100.1
* read-only, clean, young 01..1...0...01 -> 101.000101.1
* read-only, dirty, old 10..1...1...01 -> 111.000110.1
* read-only, dirty, young 11..1...0...01 -> 101.000111.1
* read-write, clean, old 00..1...1...11 -> 111.001100.1
* read-write, clean, young 01..1...0...11 -> 101.001101.1
* read-write, dirty, old 10..0...1...11 -> 110.001110.1
* read-write, dirty, young 11..0...0...11 -> 100.001111.1
* HW-bits: R read-only, I invalid
* SW-bits: p present, y young, d dirty, r read, w write, s special,
* u unused, l large
*/
if (present) {
pte_val(pte) = rste & _SEGMENT_ENTRY_ORIGIN_LARGE;
pte_val(pte) |= _PAGE_LARGE | _PAGE_PRESENT;
pte_val(pte) |= move_set_bit(rste, _SEGMENT_ENTRY_READ,
_PAGE_READ);
pte_val(pte) |= move_set_bit(rste, _SEGMENT_ENTRY_WRITE,
_PAGE_WRITE);
pte_val(pte) |= move_set_bit(rste, _SEGMENT_ENTRY_INVALID,
_PAGE_INVALID);
pte_val(pte) |= move_set_bit(rste, _SEGMENT_ENTRY_PROTECT,
_PAGE_PROTECT);
pte_val(pte) |= move_set_bit(rste, _SEGMENT_ENTRY_DIRTY,
_PAGE_DIRTY);
pte_val(pte) |= move_set_bit(rste, _SEGMENT_ENTRY_YOUNG,
_PAGE_YOUNG);
#ifdef CONFIG_MEM_SOFT_DIRTY
pte_val(pte) |= move_set_bit(rste, _SEGMENT_ENTRY_SOFT_DIRTY,
_PAGE_DIRTY);
#endif
} else
pte_val(pte) = _PAGE_INVALID;
return pte;
}
void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
pte_t *ptep, pte_t pte)
{
unsigned long rste = __pte_to_rste(pte);
/* Set correct table type for 2G hugepages */
if ((pte_val(*ptep) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3)
rste |= _REGION_ENTRY_TYPE_R3 | _REGION3_ENTRY_LARGE;
else
rste |= _SEGMENT_ENTRY_LARGE;
pte_val(*ptep) = rste;
}
pte_t huge_ptep_get(pte_t *ptep)
{
return __rste_to_pte(pte_val(*ptep));
}
pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
unsigned long addr, pte_t *ptep)
{
pte_t pte = huge_ptep_get(ptep);
pmd_t *pmdp = (pmd_t *) ptep;
pud_t *pudp = (pud_t *) ptep;
if ((pte_val(*ptep) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3)
pudp_xchg_direct(mm, addr, pudp, __pud(_REGION3_ENTRY_EMPTY));
else
pmdp_xchg_direct(mm, addr, pmdp, __pmd(_SEGMENT_ENTRY_EMPTY));
return pte;
}
pte_t *huge_pte_alloc(struct mm_struct *mm,
unsigned long addr, unsigned long sz)
{
pgd_t *pgdp;
pud_t *pudp;
pmd_t *pmdp = NULL;
pgdp = pgd_offset(mm, addr);
pudp = pud_alloc(mm, pgdp, addr);
if (pudp) {
if (sz == PUD_SIZE)
return (pte_t *) pudp;
else if (sz == PMD_SIZE)
pmdp = pmd_alloc(mm, pudp, addr);
}
return (pte_t *) pmdp;
}
pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
{
pgd_t *pgdp;
pud_t *pudp;
pmd_t *pmdp = NULL;
pgdp = pgd_offset(mm, addr);
if (pgd_present(*pgdp)) {
pudp = pud_offset(pgdp, addr);
if (pud_present(*pudp)) {
if (pud_large(*pudp))
return (pte_t *) pudp;
pmdp = pmd_offset(pudp, addr);
}
}
return (pte_t *) pmdp;
}
int pmd_huge(pmd_t pmd)
{
return pmd_large(pmd);
}
int pud_huge(pud_t pud)
{
return pud_large(pud);
}
struct page *
follow_huge_pud(struct mm_struct *mm, unsigned long address,
pud_t *pud, int flags)
{
if (flags & FOLL_GET)
return NULL;
return pud_page(*pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
}
static __init int setup_hugepagesz(char *opt)
{
unsigned long size;
char *string = opt;
size = memparse(opt, &opt);
if (MACHINE_HAS_EDAT1 && size == PMD_SIZE) {
hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
} else if (MACHINE_HAS_EDAT2 && size == PUD_SIZE) {
hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
} else {
pr_err("hugepagesz= specifies an unsupported page size %s\n",
string);
return 0;
}
return 1;
}
__setup("hugepagesz=", setup_hugepagesz);
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