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b=qAjG9wWKFtPV9NXS9taO6Yiy5MUnivAviihZaL24nX9D+axPsZSFyrVpkQFN5UGQN XFNoNSbmAcl8c7IH6DY9o3YnBFOc1Dw22mQSoVgdN9mecPwWH3AV0keCj7KBxCEbWf wBgOzIj8VSVBkIKI4MWntYqvHpS+aS4NlAHiwXO255mFXwlzKlPKOZBCkJEUX5qSQ6 tk5sehdDv4tqFgxADq73ZIuMNZrKPe+imDA/E1WLDZmrt8jFrHUZfDWOiWV4YWKVuD Epa/nui8dHaQDCQjXt8a2eMuAC/Gy18XDVfh2KqohuQL+QfGWzgbTqfjBeTz4NUZbm vwnEe//dG767w== Message-ID: <1a1cc83b-5b2a-44cc-b9e2-a31dff7ff887@kernel.org> Date: Wed, 8 Apr 2026 14:25:18 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC V1 09/16] arm64/mm: Route all pgtable reads via ptdesc_get() To: Anshuman Khandual , Mike Rapoport Cc: linux-arm-kernel@lists.infradead.org, Catalin Marinas , Will Deacon , Ryan Roberts , Mark Rutland , Lorenzo Stoakes , Andrew Morton , Linu Cherian , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20260224051153.3150613-1-anshuman.khandual@arm.com> <20260224051153.3150613-10-anshuman.khandual@arm.com> <7f7130d0-f348-451e-960e-b7e6ae9c9ee7@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4C43DC000A X-Stat-Signature: 9p5smzunmx5kuh3r1npmeq73r8yo6efk X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1775651123-6426 X-HE-Meta: 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 k01rceRC LFG3dyy2lF5xZAnL+K4asvSN94fDWlqrfCtCt06hT2lWQuWtNABtumZhdejK6j6nsEOnGi9VqFzRqwCAZpSF8b5lUFj7VElC78DmccgmBGqtBqNY/4FjnPAJ0FzpRK30dAiwKL5HeqQIXIQtmliCp0FOUcAOBLCnvGE7BOgVYO40x2Qkaq+gAS8hmN/ggxz9tKG2N8/CuuGIAGfey+giahWClChmB74W2jx7aDkX7bNV5ZS2hfkTv2+Ume2zQEY3nZz6A0PDA0vkMLrELHw84Hlh4OmXZWG3UgczW88UzYo+81YHj7TA0Ndfg61BoI29pe9i3ItDrAu4DTGhybxie9nJLEZeJuR28cQKQN+1VlflxI2Cu5Z3WsfVfwxY+4U5lKhkQQ4SQbRRKK6BbUc3nl7CUmKVf1DJ441JnZYHcQ3lMvW1gAiFijWm9ItiP+n7FAi6q Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/2/26 05:34, Anshuman Khandual wrote: > > > On 28/02/26 4:47 PM, Mike Rapoport wrote: >> Hi Anshuman, >> >> On Tue, Feb 24, 2026 at 10:41:46AM +0530, Anshuman Khandual wrote: >>> Define arm64 platform specific implementations for new pXdp_get() helpers. >>> These resolve into READ_ONCE(), thus ensuring required single copy atomic >>> semantics for the page table entry reads. >>> >>> 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 >>> --- >>> arch/arm64/include/asm/pgtable.h | 28 +++++++++++++++++++++++++++- >>> 1 file changed, 27 insertions(+), 1 deletion(-) >>> >>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h >>> index 257af1c3015d..804ef49aea88 100644 >>> --- a/arch/arm64/include/asm/pgtable.h >>> +++ b/arch/arm64/include/asm/pgtable.h >>> @@ -84,6 +84,32 @@ static inline void arch_leave_lazy_mmu_mode(void) >>> arch_flush_lazy_mmu_mode(); >>> } >>> >>> +#define ptdesc_get(x) READ_ONCE(x) >> >> This will be confusing with 'struct ptdesc' APIs, maybe ptent_get()? > > Created 'ptdesc_t' earlier on arm64 platform as an unified data type, which could > represent page table entries including their protection fields and masks for any > level. > > typedef u64 ptdesc_t; > > typedef ptdesc_t pteval_t; > typedef ptdesc_t pmdval_t; > typedef ptdesc_t pudval_t; > typedef ptdesc_t p4dval_t; > typedef ptdesc_t pgdval_t; > > But now it conflicts with generic 'struct ptdesc'. Agreed that overall renaming is > required. Probably ptent_t along with ptent_get/set() could be an option. But that > is probably orthogonal to the series and can be done later in a separate patch. We often refer to *ptep as ptent. Can we find something that does not contain "pte" to avoid confusion with pteval_t ? We often refer to the set of functions as "pXX" or "pxx". pxxval_t would certainly be an option, but it would be the first "official" such occurrence. -- Cheers, David