linux-kernel - Re: [PATCH v1 4/7] arm64/pgtable: support __HAVE_ARCH_PTE_SWP

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Message-ID: <YjRt7DqDFJRZA7Gt@arm.com>
Date:   Fri, 18 Mar 2022 11:33:00 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        John Hubbard <jhubbard@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Yang Shi <shy828301@...il.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Nadav Amit <namit@...are.com>, Rik van Riel <riel@...riel.com>,
        Roman Gushchin <guro@...com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Peter Xu <peterx@...hat.com>,
        Donald Dutile <ddutile@...hat.com>,
        Christoph Hellwig <hch@....de>,
        Oleg Nesterov <oleg@...hat.com>, Jan Kara <jack@...e.cz>,
        Liang Zhang <zhangliang5@...wei.com>,
        Pedro Gomes <pedrodemargomes@...il.com>,
        Oded Gabbay <oded.gabbay@...il.com>,
        Will Deacon <will@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, linux-mm@...ck.org,
        x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH v1 4/7] arm64/pgtable: support
 __HAVE_ARCH_PTE_SWP_EXCLUSIVE

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@....com>