linux-kernel - [PATCH] LoongArch: let pmd_present return true when splitting pmd

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Date:   Wed, 24 May 2023 15:41:32 +0800
From:   Hongchen Zhang <zhanghongchen@...ngson.cn>
To:     Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Hongchen Zhang <zhanghongchen@...ngson.cn>,
        David Hildenbrand <david@...hat.com>,
        Mike Rapoport <rppt@...nel.org>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Feiyang Chen <chenfeiyang@...ngson.cn>,
        Qi Zheng <zhengqi.arch@...edance.com>
Cc:     loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
        loongson-kernel@...ts.loongnix.cn
Subject: [PATCH] LoongArch: let pmd_present return true when splitting pmd

when we split a pmd into ptes, pmd_present() and pmd_trans_huge() should
return true,otherwise it would be treated as a swap pmd.
As arm64 does in
commit b65399f6111b ("arm64/mm: Change THP helpers to comply with generic MM semantics")
we add a _PAGE_PRESENT_INVALID bit for LoongArch.

Signed-off-by: Hongchen Zhang <zhanghongchen@...ngson.cn>
---
 arch/loongarch/include/asm/pgtable-bits.h | 2 ++
 arch/loongarch/include/asm/pgtable.h      | 3 ++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/loongarch/include/asm/pgtable-bits.h b/arch/loongarch/include/asm/pgtable-bits.h
index 8b98d22a145b..a7469d28d9d0 100644
--- a/arch/loongarch/include/asm/pgtable-bits.h
+++ b/arch/loongarch/include/asm/pgtable-bits.h
@@ -22,12 +22,14 @@
 #define	_PAGE_PFN_SHIFT		12
 #define	_PAGE_SWP_EXCLUSIVE_SHIFT 23
 #define	_PAGE_PFN_END_SHIFT	48
+#define _PAGE_PRESENT_INVALID_SHIFT 60
 #define	_PAGE_NO_READ_SHIFT	61
 #define	_PAGE_NO_EXEC_SHIFT	62
 #define	_PAGE_RPLV_SHIFT	63
 
 /* Used by software */
 #define _PAGE_PRESENT		(_ULCAST_(1) << _PAGE_PRESENT_SHIFT)
+#define _PAGE_PRESENT_INVALID	(_ULCAST_(1) << _PAGE_PRESENT_INVALID_SHIFT)
 #define _PAGE_WRITE		(_ULCAST_(1) << _PAGE_WRITE_SHIFT)
 #define _PAGE_ACCESSED		(_ULCAST_(1) << _PAGE_ACCESSED_SHIFT)
 #define _PAGE_MODIFIED		(_ULCAST_(1) << _PAGE_MODIFIED_SHIFT)
diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h
index d28fb9dbec59..9a9f9ff9b709 100644
--- a/arch/loongarch/include/asm/pgtable.h
+++ b/arch/loongarch/include/asm/pgtable.h
@@ -213,7 +213,7 @@ static inline int pmd_bad(pmd_t pmd)
 static inline int pmd_present(pmd_t pmd)
 {
 	if (unlikely(pmd_val(pmd) & _PAGE_HUGE))
-		return !!(pmd_val(pmd) & (_PAGE_PRESENT | _PAGE_PROTNONE));
+		return !!(pmd_val(pmd) & (_PAGE_PRESENT | _PAGE_PROTNONE | _PAGE_PRESENT_INVALID));
 
 	return pmd_val(pmd) != (unsigned long)invalid_pte_table;
 }
@@ -558,6 +558,7 @@ static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
 
 static inline pmd_t pmd_mkinvalid(pmd_t pmd)
 {
+	pmd_val(pmd) |= _PAGE_PRESENT_INVALID;
 	pmd_val(pmd) &= ~(_PAGE_PRESENT | _PAGE_VALID | _PAGE_DIRTY | _PAGE_PROTNONE);
 
 	return pmd;

base-commit: f1fcbaa18b28dec10281551dfe6ed3a3ed80e3d6
-- 
2.31.1