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Sat, 13 Dec 2025 00:01:22 -0800 (PST) Received: from localhost.localdomain ([45.142.165.134]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-29f05287fa3sm53149155ad.5.2025.12.13.00.01.11 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 13 Dec 2025 00:01:21 -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 RFC 2/3] x86/mm: implement redundant IPI elimination for PMD unsharing Date: Sat, 13 Dec 2025 16:00:24 +0800 Message-ID: <20251213080038.10917-3-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20251213080038.10917-1-lance.yang@linux.dev> References: <20251213080038.10917-1-lance.yang@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 3C06D1A000D X-Stat-Signature: dwx1jrwo6u4ks7phri4c7cqkbc5a3rdm X-HE-Tag: 1765612883-92164 X-HE-Meta: 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 rb74E24b 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 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 Pass both freed_tables and unshared_tables to flush_tlb_mm_range() to ensure lazy-TLB CPUs receive IPIs and flush their paging-structure caches: flush_tlb_mm_range(..., freed_tables || unshared_tables); Implement tlb_table_flush_implies_ipi_broadcast() for x86: on native x86 without paravirt or INVLPGB, the TLB flush IPI already provides necessary synchronization, allowing the second IPI to be skipped. For paravirt with non-native flush_tlb_multi and for INVLPGB, conservatively keep both IPIs. Suggested-by: David Hildenbrand (Red Hat) Signed-off-by: Lance Yang --- arch/x86/include/asm/tlb.h | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/tlb.h b/arch/x86/include/asm/tlb.h index 866ea78ba156..96602b7b7210 100644 --- a/arch/x86/include/asm/tlb.h +++ b/arch/x86/include/asm/tlb.h @@ -5,10 +5,24 @@ #define tlb_flush tlb_flush static inline void tlb_flush(struct mmu_gather *tlb); +#define tlb_table_flush_implies_ipi_broadcast tlb_table_flush_implies_ipi_broadcast +static inline bool tlb_table_flush_implies_ipi_broadcast(void); + #include #include #include #include +#include + +static inline bool tlb_table_flush_implies_ipi_broadcast(void) +{ +#ifdef CONFIG_PARAVIRT + /* Paravirt may use hypercalls that don't send real IPIs. */ + if (pv_ops.mmu.flush_tlb_multi != native_flush_tlb_multi) + return false; +#endif + return !cpu_feature_enabled(X86_FEATURE_INVLPGB); +} static inline void tlb_flush(struct mmu_gather *tlb) { @@ -20,7 +34,8 @@ static inline void tlb_flush(struct mmu_gather *tlb) end = tlb->end; } - flush_tlb_mm_range(tlb->mm, start, end, stride_shift, tlb->freed_tables); + flush_tlb_mm_range(tlb->mm, start, end, stride_shift, + tlb->freed_tables || tlb->unshared_tables); } static inline void invlpg(unsigned long addr) -- 2.49.0