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Mon, 29 Dec 2025 06:37:59 -0800 (PST) Received: from EBJ9932692.tcent.cn ([45.8.220.167]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2a2f3d7736fsm279669625ad.92.2025.12.29.06.37.50 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 29 Dec 2025 06:37:58 -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 22:36:55 +0800 Message-ID: <20251229143657.76968-2-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20251229143657.76968-1-lance.yang@linux.dev> References: <20251229143657.76968-1-lance.yang@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: 51diczge5nhaskua3b1tqgaoe6djek55 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 468841C0006 X-Rspam-User: X-HE-Tag: 1767019081-558736 X-HE-Meta: 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 Wcb2G6Mi 37Z0XQGCwDrO0XBDHlyR5I17Tie4R70ucyjgabGtiCUDUeAdp4VOrt0yIbViXdaXGe8CEFETjY/RMxIwbP77iK9ChibKq06+pS7EAhbuUZsIXYJZdt6pkLHrSOJ9y0oAaJLgfQ13lmJyt6iO0NaTNe31e0KI1xf8QN8CkGgX119MJ/buwt7aTRjuow059BF5AbRPayohpuLZYiyEafsFZDdLA/2FFgJ9Q0RLqJ7jBlC8UmnKwNTJIRNSYLzoAT0/9T6rJeFnx2rqhJ2YeLrWWkISJC25vFgukKQo25hs70w81C0DJI05JnGG+xAlsKgngcDcxv5SrPWFEdZhyY1QKXCXGwo+0gtUTbubDf1h8bG7X3PChnVoDFoD36jLODQ51l8QfkB2miD4Av2Q= 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