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Wed, 04 Nov 2026 22:12:51 -0800 (PST) Received: from G6L4RL2QG9.bytedance.net ([61.213.176.8]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3b0b323a1fdsm2107528a91.5.2026.11.04.22.12.46 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 04 Nov 2026 22:12:51 -0800 (PST) From: Muchun Song To: David Hildenbrand , Madhavan Srinivasan , Mike Rapoport , Andrew Morton Cc: Lance Yang , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Ritesh Harjani , Shrikanth Hegde , Oscar Salvador , Qi Zheng , Muchun Song , Huacai Chen , WANG Xuerui , linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-riscv@lists.infradead.org, x86@kernel.org, loongarch@lists.linux.dev, linux-s390@vger.kernel.org, Muchun Song Subject: [PATCH v2 3/5] loongarch/mm: disable device DAX vmemmap optimization Date: Thu, 5 Nov 2026 14:12:15 +0800 Message-ID: <20261105061217.13302-4-songmuchun@bytedance.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20261105061217.13302-1-songmuchun@bytedance.com> References: <20261105061217.13302-1-songmuchun@bytedance.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit LoongArch selects ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP but not ARCH_WANT_OPTIMIZE_DAX_VMEMMAP. Its vmemmap_free() implementation is also empty, so it cannot tear down optimized Device DAX mappings. A later change removes the generic Device DAX architecture gate and lets vmemmap_populate() decide whether a section can use optimization. Clear the section compound order in the LoongArch path so Device DAX keeps using unoptimized mappings. This does not affect HugeTLB HVO: LoongArch does not support gigantic pages, so HugeTLB does not use section-based vmemmap optimization there. Signed-off-by: Muchun Song --- v2: - New patch using section_vmemmap_optimization_disable() to keep Device DAX vmemmap optimization disabled on LoongArch (reported by Sashiko) --- arch/loongarch/mm/init.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/loongarch/mm/init.c b/arch/loongarch/mm/init.c index f801f7097f03..ea769e479241 100644 --- a/arch/loongarch/mm/init.c +++ b/arch/loongarch/mm/init.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include @@ -143,6 +144,7 @@ void __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node, int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node, struct vmem_altmap *altmap) { + section_vmemmap_optimization_disable(start, end); #if CONFIG_PGTABLE_LEVELS == 2 return vmemmap_populate_basepages(start, end, node, NULL); #else -- 2.54.0