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Mon, 26 Jan 2026 01:27:35 -0800 (PST) Date: Mon, 26 Jan 2026 10:26:35 +0100 In-Reply-To: <20260126092630.1800589-12-ardb+git@google.com> Mime-Version: 1.0 References: <20260126092630.1800589-12-ardb+git@google.com> X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-Developer-Signature: v=1; a=openpgp-sha256; l=1290; i=ardb@kernel.org; h=from:subject; bh=EuE34ANBL0zVmq4k3+FqMRHYv5MWLB6u2FtpmZwmAd0=; b=owGbwMvMwCVmkMcZplerG8N4Wi2JIbPc2NP6wE/2nDvLTPL8JZbbO+74uCDvbPXcOZ0xtqJM7 MeUfvR3lLIwiHExyIopsgjM/vtu5+mJUrXOs2Rh5rAygQxh4OIUgInEWjH89zjjYLlk9/MzAj/s Ld5fusylOnFKjwdb/sa9yiqHVKNkJRgZ5gZzSKnMy3t55rdrWm7btM+br+6/bMRvz21dEsYnZdv NAgA= X-Mailer: git-send-email 2.52.0.457.g6b5491de43-goog Message-ID: <20260126092630.1800589-16-ardb+git@google.com> Subject: [PATCH v2 04/10] arm64: mm: Preserve existing table mappings when mapping DRAM From: Ard Biesheuvel To: linux-kernel@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org, will@kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com, Ard Biesheuvel , Ryan Roberts , Anshuman Khandual , Liz Prucka , Seth Jenkins , Kees Cook , linux-hardening@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260126_012737_512655_41062AEF X-CRM114-Status: GOOD ( 11.91 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Ard Biesheuvel Instead of blindly overwriting an existing table entry when mapping DRAM regions, take care not to replace a pre-existing table entry with a block entry. This permits the logic of mapping the kernel's linear alias to be simplified in a subsequent patch. Signed-off-by: Ard Biesheuvel --- arch/arm64/mm/mmu.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 9d39de3cfe67..28cc3cda042c 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -262,7 +262,8 @@ static int init_pmd(pmd_t *pmdp, unsigned long addr, unsigned long end, /* try section mapping first */ if (((addr | next | phys) & ~PMD_MASK) == 0 && - (flags & NO_BLOCK_MAPPINGS) == 0) { + (flags & NO_BLOCK_MAPPINGS) == 0 && + !pmd_table(old_pmd)) { pmd_set_huge(pmdp, phys, prot); /* @@ -385,7 +386,8 @@ static int alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end, */ if (pud_sect_supported() && ((addr | next | phys) & ~PUD_MASK) == 0 && - (flags & NO_BLOCK_MAPPINGS) == 0) { + (flags & NO_BLOCK_MAPPINGS) == 0 && + !pud_table(old_pud)) { pud_set_huge(pudp, phys, prot); /* -- 2.52.0.457.g6b5491de43-goog