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powerpc/nohash/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE

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Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE on 32bit and 64bit.

On 64bit, let's use MSB 56 (LSB 7), located right next to the page type. 
On 32bit, let's use LSB 2 to avoid stealing one bit from the swap offset.

There seems to be no real reason why these bits cannot be used for swap
PTEs.  The important part is that _PAGE_PRESENT and _PAGE_HASHPTE remain
0.

While at it, mask the type in __swp_entry() and remove _PAGE_BIT_SWAP_TYPE
from pte-e500.h: while it was used in 64bit code it was ignored in 32bit
code.

Link: https://lkml.kernel.org/r/20230113171026.582290-19-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand
2023-01-13 18:10:18 +01:00
committed by Andrew Morton
parent 8897ebff37
commit 2bba2ffbe0
7 changed files with 63 additions and 28 deletions
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24
arch/powerpc/include/asm/nohash/64/pgtable.h
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@@ -276,22 +276,40 @@ static inline void __ptep_set_access_flags(struct vm_area_struct *vma,
#define pgd_ERROR(e) \
pr_err("%s:%d: bad pgd %08lx.\n", __FILE__, __LINE__, pgd_val(e))
/* Encode and de-code a swap entry */
/*
* Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
* are !pte_none() && !pte_present().
*
* Format of swap PTEs:
*
* 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* <-------------------------- offset ----------------------------
*
* 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 5 5 5 5 5 5 5 5 5 5 6 6 6 6
* 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
* --------------> <----------- zero ------------> E < type -> 0 0
*
* E is the exclusive marker that is not stored in swap entries.
*/
#define MAX_SWAPFILES_CHECK() do { \
BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > SWP_TYPE_BITS); \
} while (0)
#define SWP_TYPE_BITS 5
#define __swp_type(x) (((x).val >> _PAGE_BIT_SWAP_TYPE) \
#define __swp_type(x) (((x).val >> 2) \
& ((1UL << SWP_TYPE_BITS) - 1))
#define __swp_offset(x) ((x).val >> PTE_RPN_SHIFT)
#define __swp_entry(type, offset) ((swp_entry_t) { \
((type) << _PAGE_BIT_SWAP_TYPE) \
(((type) & 0x1f) << 2) \
| ((offset) << PTE_RPN_SHIFT) })
#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val((pte)) })
#define __swp_entry_to_pte(x) __pte((x).val)
/* We borrow MSB 56 (LSB 7) to store the exclusive marker in swap PTEs. */
#define _PAGE_SWP_EXCLUSIVE 0x80
int map_kernel_page(unsigned long ea, unsigned long pa, pgprot_t prot);
void unmap_kernel_page(unsigned long va);
extern int __meminit vmemmap_create_mapping(unsigned long start,