Re: [PATCH v2 6/8] s390/pgtable: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE

Gerald Schaefer
2022-03-30T16:50:16Z

On Tue, 29 Mar 2022 18:43:27 +0200
David Hildenbrand <david@redhat.com> wrote:

> Let's use bit 52, which is unused.
>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> arch/s390/include/asm/pgtable.h | 23 +++++++++++++++++++++--
> 1 file changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
> index 3982575bb586..a397b072a580 100644
> --- a/arch/s390/include/asm/pgtable.h
> +++ b/arch/s390/include/asm/pgtable.h
> @@ -181,6 +181,8 @@ static inline int is_module_addr(void *addr)
> #define _PAGE_SOFT_DIRTY 0x000
> #endif
>
> +#define _PAGE_SWP_EXCLUSIVE _PAGE_LARGE /* SW pte exclusive swap bit */
> +
> /* Set of bits not changed in pte_modify */
> #define _PAGE_CHG_MASK (PAGE_MASK | _PAGE_SPECIAL | _PAGE_DIRTY | \
> _PAGE_YOUNG | _PAGE_SOFT_DIRTY)
> @@ -826,6 +828,22 @@ static inline int pmd_protnone(pmd_t pmd)
> }
> #endif
>
> +#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)
> +{
> + return set_pte_bit(pte, __pgprot(_PAGE_SWP_EXCLUSIVE));
> +}
> +
> +static inline pte_t pte_swp_clear_exclusive(pte_t pte)
> +{
> + return clear_pte_bit(pte, __pgprot(_PAGE_SWP_EXCLUSIVE));
> +}
> +
> static inline int pte_soft_dirty(pte_t pte)
> {
> return pte_val(pte) & _PAGE_SOFT_DIRTY;
> @@ -1715,14 +1733,15 @@ static inline int has_transparent_hugepage(void)
> * Bits 54 and 63 are used to indicate the page type. Bit 53 marks the pte
> * as invalid.
> * A swap pte is indicated by bit pattern (pte & 0x201) == 0x200
> - * | offset |X11XX|type |S0|
> + * | offset |E11XX|type |S0|
> * |0000000000111111111122222222223333333333444444444455|55555|55566|66|
> * |0123456789012345678901234567890123456789012345678901|23456|78901|23|
> *
> * Bits 0-51 store the offset.
> + * Bit 52 (E) is used to remember PG_anon_exclusive.
> * Bits 57-61 store the type.
> * Bit 62 (S) is used for softdirty tracking.
> - * Bits 52, 55 and 56 (X) are unused.
> + * Bits 55 and 56 (X) are unused.
> */
>
> #define __SWP_OFFSET_MASK ((1UL << 52) - 1)

Thanks David!

Reviewed-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>