linux-kernel - [PATCH v15 10/13] powerpc: mm: Add pud

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Message-ID: <20250625063753.77511-11-ajd@linux.ibm.com>
Date: Wed, 25 Jun 2025 16:37:50 +1000
From: Andrew Donnellan <ajd@...ux.ibm.com>
To: linuxppc-dev@...ts.ozlabs.org, pasha.tatashin@...een.com,
        akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-riscv@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
        linux-mm@...ck.org, sweettea-kernel@...miny.me,
        christophe.leroy@...roup.eu, mingo@...nel.org
Subject: [PATCH v15 10/13] powerpc: mm: Add pud_pfn() stub

From: Rohan McLure <rmclure@...ux.ibm.com>

The page table check feature requires that pud_pfn() be defined
on each consuming architecture.

On powerpc, only book3s64 platforms allow for hugepages at this upper
level, and thus only book3s64 currently defines pud_pfn().

The page table check code that calls pud_pfn() is gated by a call to
pud_user_accessible_page(), which will always return false on any platform
other than book3s64.

Add a stub implementation of pud_pfn() for all platforms other than
book3s64. As it will never actually be used and should always be compiled
out, raise a BUILD_BUG() error.

[ajd@...ux.ibm.com: clarify commit message]
Signed-off-by: Rohan McLure <rmclure@...ux.ibm.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@...een.com>
Signed-off-by: Andrew Donnellan <ajd@...ux.ibm.com>
---
v15: clarify commit message
---
 arch/powerpc/include/asm/pgtable.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index 93d77ad5a92f..0f73a9ade0ed 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -214,6 +214,15 @@ static inline bool arch_supports_memmap_on_memory(unsigned long vmemmap_size)
 
 #endif /* CONFIG_PPC64 */
 
+#ifndef pud_pfn
+#define pud_pfn pud_pfn
+static inline int pud_pfn(pud_t pud)
+{
+	BUILD_BUG();
+	return 0;
+}
+#endif
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_POWERPC_PGTABLE_H */
-- 
2.49.0