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Mon, 29 Dec 2025 06:54:46 -0800 (PST) Received: from EBJ9932692.tcent.cn ([103.88.46.167]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-34e70dbcb6esm31557603a91.9.2025.12.29.06.54.38 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 29 Dec 2025 06:54:46 -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 v2 1/3] mm/tlb: allow architectures to skip redundant TLB sync IPIs Date: Mon, 29 Dec 2025 22:52:43 +0800 Message-ID: <20251229145245.85452-2-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20251229145245.85452-1-lance.yang@linux.dev> References: <20251229145245.85452-1-lance.yang@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Stat-Signature: 939e6m6oq4hpdf7ca93adzjbr98xzc3i X-Rspam-User: X-Rspamd-Queue-Id: D214440002 X-HE-Tag: 1767020087-116874 X-HE-Meta: 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 YVaDlAjY 9XHFuBUjsv66OXvkh04Zh6n7dOS9KZa823eWr99L+MtNeg+vyouAZ5OWyXrP0fRXH7bJOMXnLrIPU50N9ch+H0FyRtlAx6GWqq5RC9SloU4yBa0/yFpPSktyC0YCSenklB92q9lkQg+1xWhh71w2DMfrbHnS52/2UZ+8/LRWaMigiFKgrAFBNVEsjKrhN1+ep/nmhQptP4gnRF0AfjZmWtjs7Eald04/ZDTUZluZYpba9lqUVRwCUDHBqSXBvEKinTUjNCKH2hdug2Ruu9WjNuOYiMaNWHHbP80NpUrU2gy5NXPwY5owwAwYI1kT7P0RPO7oT1QLeDwT/mSS+BckDWfDX1EcIIFCcvYTeiVf/LUsYRSKGjH5law6xCfAfMzpLthNq/kOUsmX+sAGiFvVhy7Jf40ReXPoZ+Pp00H1L/FA/QSOA6N4j8KC93282zxXoU442WkIOSeMw4Ccz/Ld9o/c8LQ== 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