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Mon, 29 Dec 2025 06:31:01 -0800 (PST) Received: from EBJ9932692.tcent.cn ([103.88.46.167]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7ff7dfac28fsm29705159b3a.32.2025.12.29.06.30.52 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 29 Dec 2025 06:31:01 -0800 (PST) From: Lance Yang To: akpm@linux-foundation.org Cc: will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, arnd@arndb.de, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, ioworker0@gmail.com, shy828301@gmail.com, riel@surriel.com, jannh@google.com, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Lance Yang Subject: [PATCH RESEND v1 1/3] mm/tlb: allow architectures to skip redundant TLB sync IPIs Date: Mon, 29 Dec 2025 22:30:31 +0800 Message-ID: <20251229143038.73315-2-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20251229143038.73315-1-lance.yang@linux.dev> References: <20251229143038.73315-1-lance.yang@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: D5A03180019 X-Stat-Signature: 51diczge5nhaskua3b1tqgaoe6djek55 X-Rspam-User: X-HE-Tag: 1767018662-238499 X-HE-Meta: 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 +D8bv69B 3rxO6a12UPejZHxD4QwjlzbykNewBfvKlU824DV++mevzJDpp6TaMQvjccBEvo1KjLa4pld+XgideI6pKDt+X3KWux2PZYl0fr6Nx9v1gVsZlueR/x8NQ7Gf7gBrZzNQKod4nGl/omlY2oSVktKVAuY6Tulv9TBoci+y5VSmNF1nlgOwESG4Km8InTe614sQqFMl660dCRA1gTCkgqnGSMAfXgkj5FWbVdOMsU2qGTTBYLJ17xSY1fZ1doIUooXDfzkc+7//w6k4emxBcufWtXmnVJ98tzsdnFuM3xAQUu4PKKsy+159o6GSIJIV7FISB8Wj1K/h4bD3qlbx8QsP9f+kJVJSYPBIPnEOBg0XleKETPDnW0N3BfX9HdYvg7yuUygZKgbHutklkIn0= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Lance Yang When unsharing hugetlb PMD page tables, we currently send two IPIs: one for TLB invalidation, and another to synchronize with concurrent GUP-fast walkers. However, if the TLB flush already reaches all CPUs, the second IPI is redundant. GUP-fast runs with IRQs disabled, so when the TLB flush IPI completes, any concurrent GUP-fast must have finished. Add tlb_table_flush_implies_ipi_broadcast() to let architectures indicate their TLB flush provides full synchronization, enabling the redundant IPI to be skipped. Suggested-by: David Hildenbrand (Red Hat) Signed-off-by: Lance Yang --- include/asm-generic/tlb.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h index 4d679d2a206b..e8d99b5e831f 100644 --- a/include/asm-generic/tlb.h +++ b/include/asm-generic/tlb.h @@ -261,6 +261,20 @@ static inline void tlb_remove_table_sync_one(void) { } #endif /* CONFIG_MMU_GATHER_RCU_TABLE_FREE */ +/* + * Architectures can override if their TLB flush already broadcasts IPIs to all + * CPUs when freeing or unsharing page tables. + * + * Return true only when the flush guarantees: + * - IPIs reach all CPUs with potentially stale paging-structure cache entries + * - Synchronization with IRQ-disabled code like GUP-fast + */ +#ifndef tlb_table_flush_implies_ipi_broadcast +static inline bool tlb_table_flush_implies_ipi_broadcast(void) +{ + return false; +} +#endif #ifndef CONFIG_MMU_GATHER_NO_GATHER /* -- 2.49.0