Re: [PATCH v1 4/7] arm64/pgtable: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE

From: Catalin Marinas <catalin.marinas@arm.com>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Hugh Dickins <hughd@google.com>,
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	linux-arm-kernel@lists.infradead.org,
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Subject: Re: [PATCH v1 4/7] arm64/pgtable: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE
Date: Fri, 18 Mar 2022 11:33:00 +0000	[thread overview]
Message-ID: <YjRt7DqDFJRZA7Gt@arm.com> (raw)
In-Reply-To: <8989a07b-3a5b-0c81-983f-b35403d19579@redhat.com>

On Fri, Mar 18, 2022 at 10:59:10AM +0100, David Hildenbrand wrote:
> diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
> index b1e1b74d993c..fd6ddf14c190 100644
> --- a/arch/arm64/include/asm/pgtable-prot.h
> +++ b/arch/arm64/include/asm/pgtable-prot.h
> @@ -14,6 +14,7 @@
>   * Software defined PTE bits definition.
>   */
>  #define PTE_WRITE		(PTE_DBM)		 /* same as DBM (51) */
> +#define PTE_SWP_EXCLUSIVE	(PTE_TABLE_BIT)		 /* only for swp ptes */
>  #define PTE_DIRTY		(_AT(pteval_t, 1) << 55)
>  #define PTE_SPECIAL		(_AT(pteval_t, 1) << 56)
>  #define PTE_DEVMAP		(_AT(pteval_t, 1) << 57)
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 94e147e5456c..c78994073cd0 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -402,6 +402,22 @@ static inline pgprot_t mk_pmd_sect_prot(pgprot_t prot)
>  	return __pgprot((pgprot_val(prot) & ~PMD_TABLE_BIT) | PMD_TYPE_SECT);
>  }
>  
> +#define __HAVE_ARCH_PTE_SWP_EXCLUSIVE
> +static inline pte_t pte_swp_mkexclusive(pte_t pte)
> +{
> +	return set_pte_bit(pte, __pgprot(PTE_SWP_EXCLUSIVE));
> +}
> +
> +static inline int pte_swp_exclusive(pte_t pte)
> +{
> +	return pte_val(pte) & PTE_SWP_EXCLUSIVE;
> +}
> +
> +static inline pte_t pte_swp_clear_exclusive(pte_t pte)
> +{
> +	return clear_pte_bit(pte, __pgprot(PTE_SWP_EXCLUSIVE));
> +}
> +
>  #ifdef CONFIG_NUMA_BALANCING
>  /*
>   * See the comment in include/linux/pgtable.h
> @@ -908,7 +924,8 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
>  
>  /*
>   * Encode and decode a swap entry:
> - *	bits 0-1:	present (must be zero)
> + *	bits 0:		present (must be zero)
> + *	bits 1:		remember PG_anon_exclusive

It looks fine to me.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>