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csky/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE

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Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit from the
offset.  This reduces the maximum swap space per file to 16 GiB (was 32
GiB).

We might actually be able to reuse one of the other software bits
(_PAGE_READ / PAGE_WRITE) instead, because we only have to keep
pte_present(), pte_none() and HW happy.  For now, let's keep it simple
because there might be something non-obvious.

Link: https://lkml.kernel.org/r/20230113171026.582290-6-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Guo Ren <guoren@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2023-01-13 18:10:05 +01:00 committed by Andrew Morton
parent 20aae9eff5
commit 41e0d49104
3 changed files with 39 additions and 11 deletions
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13
arch/csky/abiv1/inc/abi/pgtable-bits.h
View File

@ -10,6 +10,9 @@
#define _PAGE_ACCESSED (1<<3)
#define _PAGE_MODIFIED (1<<4)
/* We borrow bit 9 to store the exclusive marker in swap PTEs. */
#define _PAGE_SWP_EXCLUSIVE (1<<9)
/* implemented in hardware */
#define _PAGE_GLOBAL (1<<6)
#define _PAGE_VALID (1<<7)
@ -26,7 +29,8 @@
#define _PAGE_PROT_NONE _PAGE_READ
/*
* Encode and decode a swap entry
* Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
* are !pte_none() && !pte_present().
*
* Format of swap PTE:
* bit 0: _PAGE_PRESENT (zero)
@ -35,15 +39,16 @@
* bit 6: _PAGE_GLOBAL (zero)
* bit 7: _PAGE_VALID (zero)
* bit 8: swap type[4]
* bit 9 - 31: swap offset
* bit 9: exclusive marker
* bit 10 - 31: swap offset
*/
#define __swp_type(x) ((((x).val >> 2) & 0xf) | \
(((x).val >> 4) & 0x10))
#define __swp_offset(x) ((x).val >> 9)
#define __swp_offset(x) ((x).val >> 10)
#define __swp_entry(type, offset) ((swp_entry_t) { \
((type & 0xf) << 2) | \
((type & 0x10) << 4) | \
((offset) << 9)})
((offset) << 10)})
#define HAVE_ARCH_UNMAPPED_AREA

19
arch/csky/abiv2/inc/abi/pgtable-bits.h
View File

@ -10,6 +10,9 @@
#define _PAGE_PRESENT (1<<10)
#define _PAGE_MODIFIED (1<<11)
/* We borrow bit 7 to store the exclusive marker in swap PTEs. */
#define _PAGE_SWP_EXCLUSIVE (1<<7)
/* implemented in hardware */
#define _PAGE_GLOBAL (1<<0)
#define _PAGE_VALID (1<<1)
@ -26,23 +29,25 @@
#define _PAGE_PROT_NONE _PAGE_WRITE
/*
* Encode and decode a swap entry
* Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
* are !pte_none() && !pte_present().
*
* Format of swap PTE:
* bit 0: _PAGE_GLOBAL (zero)
* bit 1: _PAGE_VALID (zero)
* bit 2 - 6: swap type
* bit 7 - 8: swap offset[0 - 1]
* bit 7: exclusive marker
* bit 8: swap offset[0]
* bit 9: _PAGE_WRITE (zero)
* bit 10: _PAGE_PRESENT (zero)
* bit 11 - 31: swap offset[2 - 22]
* bit 11 - 31: swap offset[1 - 21]
*/
#define __swp_type(x) (((x).val >> 2) & 0x1f)
#define __swp_offset(x) ((((x).val >> 7) & 0x3) | \
(((x).val >> 9) & 0x7ffffc))
#define __swp_offset(x) ((((x).val >> 8) & 0x1) | \
(((x).val >> 10) & 0x3ffffe))
#define __swp_entry(type, offset) ((swp_entry_t) { \
((type & 0x1f) << 2) | \
((offset & 0x3) << 7) | \
((offset & 0x7ffffc) << 9)})
((offset & 0x1) << 8) | \
((offset & 0x3ffffe) << 10)})
#endif /* __ASM_CSKY_PGTABLE_BITS_H */

18
arch/csky/include/asm/pgtable.h
View File

@ -200,6 +200,24 @@ static inline pte_t pte_mkyoung(pte_t pte)
return pte;
}
#define __HAVE_ARCH_PTE_SWP_EXCLUSIVE
static inline int pte_swp_exclusive(pte_t pte)
{
return pte_val(pte) & _PAGE_SWP_EXCLUSIVE;
}
static inline pte_t pte_swp_mkexclusive(pte_t pte)
{
pte_val(pte) |= _PAGE_SWP_EXCLUSIVE;
return pte;
}
static inline pte_t pte_swp_clear_exclusive(pte_t pte)
{
pte_val(pte) &= ~_PAGE_SWP_EXCLUSIVE;
return pte;
}
#define __HAVE_PHYS_MEM_ACCESS_PROT
struct file;
extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,