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([36.28.158.221]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-841d70f1ed8sm828385b3a.43.2026.05.26.20.56.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 May 2026 20:56:39 -0700 (PDT) From: Xueyuan chen To: akpm@linux-foundation.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org, catalin.marinas@arm.com, will@kernel.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, david@kernel.org, ljs@kernel.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, ryan.roberts@arm.com, dev.jain@arm.com, lance.yang@linux.dev, yang@os.amperecomputing.com, jannh@google.com, Xueyuan Chen Subject: [RFC PATCH 3/3] x86/mm: make huge zero folio read-only in direct map Date: Wed, 27 May 2026 11:56:07 +0800 Message-ID: <20260527035607.14919-4-xueyuan.chen21@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260527035607.14919-1-xueyuan.chen21@gmail.com> References: <20260527035607.14919-1-xueyuan.chen21@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Xueyuan Chen Implement arch_make_huge_zero_folio_readonly() for x86-64. Once allocated, try to make the folio read-only in the direct map so unexpected writes fault instead of corrupting shared zero contents. The set_memory_ro() update is best effort: if it fails, generic THP keeps using the writable persistent huge zero folio. Co-developed-by: Lance Yang Signed-off-by: Lance Yang Signed-off-by: Xueyuan Chen --- arch/x86/Kconfig | 1 + arch/x86/mm/init.c | 11 +++++++++++ 2 files changed, 12 insertions(+) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index f3f7cb01d69d..81f9478d2803 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -24,6 +24,7 @@ config X86_64 def_bool y depends on 64BIT # Options that are inherently 64-bit kernel only: + select ARCH_HAS_READONLY_HUGE_ZERO_FOLIO select ARCH_HAS_GIGANTIC_PAGE select ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index fb67217fddcd..ef721aa2ff0c 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -3,6 +3,8 @@ #include #include #include +#include +#include #include #include #include @@ -38,6 +40,15 @@ #include "mm_internal.h" +#ifdef CONFIG_READONLY_HUGE_ZERO_FOLIO +bool __init arch_make_huge_zero_folio_readonly(struct folio *folio) +{ + unsigned long addr = (unsigned long)folio_address(folio); + + return !set_memory_ro(addr, HPAGE_PMD_NR); +} +#endif + /* * Tables translating between page_cache_type_t and pte encoding. * -- 2.47.3