linux-kernel - [PATCH v4 07/16] arm64/mm: ptep_get_and_clear(): New layer to manage contig bit

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Message-Id: <20231218105100.172635-8-ryan.roberts@arm.com>
Date: Mon, 18 Dec 2023 10:50:51 +0000
From: Ryan Roberts <ryan.roberts@....com>
To: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Ard Biesheuvel <ardb@...nel.org>,
	Marc Zyngier <maz@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	James Morse <james.morse@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Vincenzo Frascino <vincenzo.frascino@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Anshuman Khandual <anshuman.khandual@....com>,
	Matthew Wilcox <willy@...radead.org>,
	Yu Zhao <yuzhao@...gle.com>,
	Mark Rutland <mark.rutland@....com>,
	David Hildenbrand <david@...hat.com>,
	Kefeng Wang <wangkefeng.wang@...wei.com>,
	John Hubbard <jhubbard@...dia.com>,
	Zi Yan <ziy@...dia.com>,
	Barry Song <21cnbao@...il.com>,
	Alistair Popple <apopple@...dia.com>,
	Yang Shi <shy828301@...il.com>
Cc: Ryan Roberts <ryan.roberts@....com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v4 07/16] arm64/mm: ptep_get_and_clear(): New layer to manage contig bit

Create a new layer for the in-table PTE manipulation APIs. For now, The
existing API is prefixed with double underscore to become the
arch-private API and the public API is just a simple wrapper that calls
the private API.

The public API implementation will subsequently be used to transparently
manipulate the contiguous bit where appropriate. But since there are
already some contig-aware users (e.g. hugetlb, kernel mapper), we must
first ensure those users use the private API directly so that the future
contig-bit manipulations in the public API do not interfere with those
existing uses.

Tested-by: John Hubbard <jhubbard@...dia.com>
Signed-off-by: Ryan Roberts <ryan.roberts@....com>
---
 arch/arm64/include/asm/pgtable.h | 5 +++--
 arch/arm64/mm/hugetlbpage.c      | 6 +++---
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 1464e990580a..994597a0bb0f 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -941,8 +941,7 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
-#define __HAVE_ARCH_PTEP_GET_AND_CLEAR
-static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
+static inline pte_t __ptep_get_and_clear(struct mm_struct *mm,
 				       unsigned long address, pte_t *ptep)
 {
 	pte_t pte = __pte(xchg_relaxed(&pte_val(*ptep), 0));
@@ -1122,6 +1121,8 @@ extern void ptep_modify_prot_commit(struct vm_area_struct *vma,
 #define set_pte					__set_pte
 #define set_ptes				__set_ptes
 #define pte_clear				__pte_clear
+#define __HAVE_ARCH_PTEP_GET_AND_CLEAR
+#define ptep_get_and_clear			__ptep_get_and_clear
 
 #endif /* !__ASSEMBLY__ */
 
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 510b2d4b89a9..c2a753541d13 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -188,7 +188,7 @@ static pte_t get_clear_contig(struct mm_struct *mm,
 	unsigned long i;
 
 	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++) {
-		pte_t pte = ptep_get_and_clear(mm, addr, ptep);
+		pte_t pte = __ptep_get_and_clear(mm, addr, ptep);
 
 		/*
 		 * If HW_AFDBM is enabled, then the HW could turn on
@@ -236,7 +236,7 @@ static void clear_flush(struct mm_struct *mm,
 	unsigned long i, saddr = addr;
 
 	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++)
-		ptep_clear(mm, addr, ptep);
+		__ptep_get_and_clear(mm, addr, ptep);
 
 	flush_tlb_range(&vma, saddr, addr);
 }
@@ -411,7 +411,7 @@ pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
 	pte_t orig_pte = ptep_get(ptep);
 
 	if (!pte_cont(orig_pte))
-		return ptep_get_and_clear(mm, addr, ptep);
+		return __ptep_get_and_clear(mm, addr, ptep);
 
 	ncontig = find_num_contig(mm, addr, ptep, &pgsize);
 
-- 
2.25.1