linux-kernel - [PATCH v6 7/9] arm64/mm: Override arch_wants_pte

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Message-Id: <20230929114421.3761121-8-ryan.roberts@arm.com>
Date:   Fri, 29 Sep 2023 12:44:18 +0100
From:   Ryan Roberts <ryan.roberts@....com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Yin Fengwei <fengwei.yin@...el.com>,
        David Hildenbrand <david@...hat.com>,
        Yu Zhao <yuzhao@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Yang Shi <shy828301@...il.com>,
        "Huang, Ying" <ying.huang@...el.com>, Zi Yan <ziy@...dia.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Itaru Kitayama <itaru.kitayama@...il.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        John Hubbard <jhubbard@...dia.com>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Hugh Dickins <hughd@...gle.com>
Cc:     Ryan Roberts <ryan.roberts@....com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v6 7/9] arm64/mm: Override arch_wants_pte_order()

Define an arch-specific override of arch_wants_pte_order() so that when
anon_orders=recommend is set, large folios will be allocated for
anonymous memory with an order that is compatible with arm64's HPA uarch
feature.

Reviewed-by: Yu Zhao <yuzhao@...gle.com>
Signed-off-by: Ryan Roberts <ryan.roberts@....com>
---
 arch/arm64/include/asm/pgtable.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 7f7d9b1df4e5..e3d2449dec5c 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -1110,6 +1110,16 @@ extern pte_t ptep_modify_prot_start(struct vm_area_struct *vma,
 extern void ptep_modify_prot_commit(struct vm_area_struct *vma,
 				    unsigned long addr, pte_t *ptep,
 				    pte_t old_pte, pte_t new_pte);
+
+#define arch_wants_pte_order arch_wants_pte_order
+static inline int arch_wants_pte_order(void)
+{
+	/*
+	 * Many arm64 CPUs support hardware page aggregation (HPA), which can
+	 * coalesce 4 contiguous pages into a single TLB entry.
+	 */
+	return 2;
+}
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_PGTABLE_H */
-- 
2.25.1