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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=MKSa8BSt9BSP9qCifI6PxRc6JlT2Rvcm3UBj7hlH3DOwlOqZ9GbA9MJXvTzduITUK cN/VxqCg7WM5rVROAvZB87oajUO9GN3RvAL+HjURwBq+pFlLCnauo53bTJRALtYeAF CU7fyXOpRpolf4zP8xtVI/2LDMhBuehQgWhWCh8s= Message-ID: Date: Wed, 27 May 2026 15:12:20 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC V2 08/14] arm64/mm: Route all pgtable writes via pxxval_set() Content-Language: en-GB To: Anshuman Khandual , linux-arm-kernel@lists.infradead.org Cc: Catalin Marinas , Will Deacon , Mark Rutland , Lorenzo Stoakes , Andrew Morton , David Hildenbrand , Mike Rapoport , Linu Cherian , Usama Arif , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20260513044547.4128549-1-anshuman.khandual@arm.com> <20260513044547.4128549-9-anshuman.khandual@arm.com> From: Ryan Roberts In-Reply-To: <20260513044547.4128549-9-anshuman.khandual@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 9otmwaeyeu98p4bu8afkyyzappm96sft X-Rspamd-Queue-Id: 3AAB980007 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1779891145-461775 X-HE-Meta: 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 S8JlFfyK M56f8i1vzUqwCQkr1YmyXUj9fPXC7Y+B2N6/mxvy8RmlvNtfSHAqIVLZPyhVhobl8GIx2ADPiX9HwZQfovhA9J6XJ0hecpG25uROXHeUDmEyqS/zWsaxkiZeVnupt8b5t7hEMR7N4KlwevUZGiqiVA/LKfLDZ2RdVmBPdSzCeaUehSAnFly8CUdj47Xd3GKRGXSiuaZqyuYWXMsvAQ9WAGLL5mWF11EBt+5pNX36tQiiBaLc2vXrE1fkdqSrJsv2Z2sYpxUkKJ1FE5xV6bvlBp60MxRf74kLb75wQsRnin5W1Dvs6P3KwV4+tRRTrc5HU9nb9YFp2i1NN61cI5+t8Sq9WagsKgrLLc1RBRG9hbQzNM6acy921SIex1Ophss2Gc3hMgiIWQMiuXzyyAJHyF6VJDkvag+HONsd9ir4zhW2Fca4= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 13/05/2026 05:45, Anshuman Khandual wrote: > Currently pxxval_set() is defined as WRITE_ONCE() but this will change for > D128 pgtable builds, for which WRITE_ONCE() is not sufficient for single > copy atomicity. > > In future this infrastructure can be used for D128 to maintain single copy > atomicity semantics with inline asm blocks. > > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Ryan Roberts > Cc: Mark Rutland > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Anshuman Khandual > --- > Changes in RFC V2: > > - Renamed all ptdesc_ instances as pxxval_ instead > > arch/arm64/include/asm/pgtable.h | 11 ++++++----- > arch/arm64/mm/mmu.c | 4 ++-- > 2 files changed, 8 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 72da582e8d12..c71bb829e9f1 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -85,6 +85,7 @@ static inline void arch_leave_lazy_mmu_mode(void) > } > > #define pxxval_get(x) READ_ONCE(x) > +#define pxxval_set(x, val) WRITE_ONCE(x, val) Same comment as for pxxval_get(): I think it would be clearer if this was an inline function that took a pointer. Thanks, Ryan > > #define pmdp_get pmdp_get > static inline pmd_t pmdp_get(pmd_t *pmdp) > @@ -385,7 +386,7 @@ static inline pte_t pte_clear_uffd_wp(pte_t pte) > > static inline void __set_pte_nosync(pte_t *ptep, pte_t pte) > { > - WRITE_ONCE(*ptep, pte); > + pxxval_set(*ptep, pte); > } > > static inline void __set_pte_complete(pte_t pte) > @@ -856,7 +857,7 @@ static inline void set_pmd(pmd_t *pmdp, pmd_t pmd) > } > #endif /* __PAGETABLE_PMD_FOLDED */ > > - WRITE_ONCE(*pmdp, pmd); > + pxxval_set(*pmdp, pmd); > > if (pmd_valid(pmd)) > queue_pte_barriers(); > @@ -921,7 +922,7 @@ static inline void set_pud(pud_t *pudp, pud_t pud) > return; > } > > - WRITE_ONCE(*pudp, pud); > + pxxval_set(*pudp, pud); > > if (pud_valid(pud)) > queue_pte_barriers(); > @@ -1003,7 +1004,7 @@ static inline void set_p4d(p4d_t *p4dp, p4d_t p4d) > return; > } > > - WRITE_ONCE(*p4dp, p4d); > + pxxval_set(*p4dp, p4d); > queue_pte_barriers(); > } > > @@ -1131,7 +1132,7 @@ static inline void set_pgd(pgd_t *pgdp, pgd_t pgd) > return; > } > > - WRITE_ONCE(*pgdp, pgd); > + pxxval_set(*pgdp, pgd); > queue_pte_barriers(); > } > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 7fbb2ef86cfa..6eb92d8f46be 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -76,7 +76,7 @@ void noinstr set_swapper_pgd(pgd_t *pgdp, pgd_t pgd) > * writable in the kernel mapping. > */ > if (rodata_is_rw) { > - WRITE_ONCE(*pgdp, pgd); > + pxxval_set(*pgdp, pgd); > dsb(ishst); > isb(); > return; > @@ -84,7 +84,7 @@ void noinstr set_swapper_pgd(pgd_t *pgdp, pgd_t pgd) > > spin_lock(&swapper_pgdir_lock); > fixmap_pgdp = pgd_set_fixmap(__pa_symbol(pgdp)); > - WRITE_ONCE(*fixmap_pgdp, pgd); > + pxxval_set(*fixmap_pgdp, pgd); > /* > * We need dsb(ishst) here to ensure the page-table-walker sees > * our new entry before set_p?d() returns. The fixmap's