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Mon, 29 Dec 2025 06:13:32 -0800 (PST) Received: from EBJ9932692.tcent.cn ([103.88.46.167]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7ff7a93ab3csm29472636b3a.7.2025.12.29.06.13.23 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 29 Dec 2025 06:13:32 -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 v1 3/3] mm: embed TLB flush IPI check in tlb_remove_table_sync_one() Date: Mon, 29 Dec 2025 22:12:45 +0800 Message-ID: <20251229141246.63435-4-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20251229141246.63435-1-lance.yang@linux.dev> References: <20251229141246.63435-1-lance.yang@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: E08C3180002 X-Stat-Signature: rhapfknoymjinire5kje4iqgfosh8jag X-HE-Tag: 1767017613-108547 X-HE-Meta: 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 3R9jKUu7 FdlVYYQmQWzxy827g5GbJf3B+y2lUkTBFP2ABvhwwEsT6VT2dpzICkiPQT5ujpl7w4kJt4marv5w+1eyaZ3Zp708IO6AOJZjxGes177hrQT3IiSPR4KoaZPpz3J2Bb0joc9e59okgNOfaWtimUMptDZE15rvLk32QZ88fgrQl3GnNq07GEn57qGN9PZ1d+5cm0qWYNp6Rqbd8XbalBuy/yer32YUJyRG1kC/mMgWDveKrBy+Py2L9lA4XGkSfo2cFTrBGo6Hq6AoDk1in/miQdKsBfGjVGg7sOfxjs8LfJ/wSGNrCBQCfwTZoeLSnDwpZTgLgWDJLd+QMsJO5PLNCyBOjIbp89yuPPS/MivDAaoHxyRKqXrycj2ogvsfZU6gYLYlabfgi1iCmKkEb4JdOsnoK/Mt0MYm2Oq3zYjYN+v8BGarP5v/AL7R+ag== 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 Embed the tlb_table_flush_implies_ipi_broadcast() check directly inside tlb_remove_table_sync_one() instead of requiring every caller to check it explicitly. This relies on callers to do the right thing: flush with freed_tables=true or unshared_tables=true beforehand. All existing callers satisfy this requirement: 1. mm/khugepaged.c:1188 (collapse_huge_page): pmdp_collapse_flush(vma, address, pmd) -> flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE) -> flush_tlb_mm_range(mm, ..., freed_tables = true) -> flush_tlb_multi(mm_cpumask(mm), info) So freed_tables=true before calling tlb_remove_table_sync_one(). 2. include/asm-generic/tlb.h:861 (tlb_flush_unshared_tables): tlb_flush_mmu_tlbonly(tlb) -> tlb_flush(tlb) -> flush_tlb_mm_range(mm, ..., unshared_tables = true) -> flush_tlb_multi(mm_cpumask(mm), info) unshared_tables=true (equivalent to freed_tables for sending IPIs). 3. mm/mmu_gather.c:341 (__tlb_remove_table_one): When we can't allocate a batch page in tlb_remove_table(), we do: tlb_table_invalidate(tlb) -> tlb_flush_mmu_tlbonly(tlb) -> flush_tlb_mm_range(mm, ..., freed_tables = true) -> flush_tlb_multi(mm_cpumask(mm), info) Then: tlb_remove_table_one(table) -> __tlb_remove_table_one(table) // if !CONFIG_PT_RECLAIM -> tlb_remove_table_sync_one() freed_tables=true, and this should work too. Why is tlb->freed_tables guaranteed? Because callers like pte_free_tlb() (via free_pte_range) set freed_tables=true before calling __pte_free_tlb(), which then calls tlb_remove_table(). We cannot free page tables without freed_tables=true. Note that tlb_remove_table_sync_one() was a NOP on bare metal x86 (CONFIG_MMU_GATHER_RCU_TABLE_FREE=n) before commit a37259732a7d ("x86/mm: Make MMU_GATHER_RCU_TABLE_FREE unconditional"). 4-5. mm/khugepaged.c:1683,1819 (pmdp_get_lockless_sync macro): Same as #1. These also use pmdp_collapse_flush() beforehand. Suggested-by: David Hildenbrand (Red Hat) Signed-off-by: Lance Yang --- mm/mmu_gather.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/mmu_gather.c b/mm/mmu_gather.c index 7468ec388455..7b588643cbae 100644 --- a/mm/mmu_gather.c +++ b/mm/mmu_gather.c @@ -276,6 +276,10 @@ static void tlb_remove_table_smp_sync(void *arg) void tlb_remove_table_sync_one(void) { + /* Skip the IPI if the TLB flush already synchronized with other CPUs. */ + if (tlb_table_flush_implies_ipi_broadcast()) + return; + /* * This isn't an RCU grace period and hence the page-tables cannot be * assumed to be actually RCU-freed. -- 2.49.0