linux-kernel - [PATCH 4/6] arm64/mm: Ensure correct 48 bit PA gets into TTBRx

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Message-Id: <20251103052618.586763-5-anshuman.khandual@arm.com>
Date: Mon,  3 Nov 2025 05:26:16 +0000
From: Anshuman Khandual <anshuman.khandual@....com>
To: linux-arm-kernel@...ts.infradead.org
Cc: Anshuman Khandual <anshuman.khandual@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Ryan Roberts <ryan.roberts@....com>,
	Ard Biesheuvel <ardb@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 4/6] arm64/mm: Ensure correct 48 bit PA gets into TTBRx_EL1

Even though 48 bit PA representation in TTBRx_EL1 does not involve shifting
partial bits like 52 bit variant does, they sill need to be masked properly
for correctness. Hence mask 48 bit PA with TTBRx_EL1_BADDR_MASK.

Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
 arch/arm64/include/asm/assembler.h | 1 +
 arch/arm64/include/asm/pgtable.h   | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 23be85d93348..d5eb09fc5f8a 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -609,6 +609,7 @@ alternative_endif
 	and	\ttbr, \ttbr, #TTBR_BADDR_MASK_52
 #else
 	mov	\ttbr, \phys
+	and	\ttbr, \ttbr, #TTBRx_EL1_BADDR_MASK
 #endif
 	.endm
 
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 0944e296dd4a..c3110040c137 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -1604,7 +1604,7 @@ static inline void update_mmu_cache_range(struct vm_fault *vmf,
 #ifdef CONFIG_ARM64_PA_BITS_52
 #define phys_to_ttbr(addr)	(((addr) | ((addr) >> 46)) & TTBR_BADDR_MASK_52)
 #else
-#define phys_to_ttbr(addr)	(addr)
+#define phys_to_ttbr(addr)	(addr & TTBRx_EL1_BADDR_MASK)
 #endif
 
 /*
-- 
2.30.2