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Mon, 29 Dec 2025 06:13:23 -0800 (PST) Received: from EBJ9932692.tcent.cn ([103.88.46.167]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7ff7a93ab3csm29472636b3a.7.2025.12.29.06.13.14 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 29 Dec 2025 06:13:23 -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 2/3] x86/mm: implement redundant IPI elimination for page table operations Date: Mon, 29 Dec 2025 22:12:44 +0800 Message-ID: <20251229141246.63435-3-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-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: AA5D21A001A X-Stat-Signature: p9mcfe99xtat951q3w9dokpz39xry157 X-Rspam-User: X-HE-Tag: 1767017604-997683 X-HE-Meta: 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 iRZXs+j5 Qwo6rAegenKBDC384X4aSGcDFnRI8e4KWY7zzcYnxADnDSDV8TM4qWaDL6Uw8uBz6dqkqK8DYhZ2J6ggXwRdAn3aSlUyeq5qy9rUTALiyfHIpTEn2qcBiLg565DkPotYslulHs4ggJDgNp+vqU8A0MH/38LXJUrDEktJsrdb/L9BKqHJVirORwABBWVQun0s6/QzN41D7IICY4DTY35WbYnpi+l9u+IblkqDWrMVXUu12y7oPhg6EMPOMYJJLyr6FezmoXRwr5o4Bcxh8M3b6F7zvkC7pla+rtTzYJwdVM6JOuxbQ4zgU0EqP5PueVzEfFj8/2AM0Mx0bm1TQVq4ftOIPeOi47JlID2Hhn/2zRcXc/j84NiSZhEHlswobaD9YUtR0fSnHyrNSSwgE/9UMBZH+KQJfpH2pwm3iHphzarITFVmK3boGnzmVdCydCdJh4nSpqfVpPZjtefaRWbLGDXrAjQ== 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 Add a callback function flush_tlb_multi_implies_ipi_broadcast to pv_mmu_ops to explicitly track whether flush_tlb_multi IPIs provide sufficient synchronization for GUP-fast when freeing or unsharing page tables. 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); Suggested-by: David Hildenbrand (Red Hat) Signed-off-by: Lance Yang --- arch/x86/include/asm/paravirt_types.h | 6 ++++++ arch/x86/include/asm/tlb.h | 19 ++++++++++++++++++- arch/x86/kernel/paravirt.c | 10 ++++++++++ 3 files changed, 34 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h index 3502939415ad..a5bd0983da1f 100644 --- a/arch/x86/include/asm/paravirt_types.h +++ b/arch/x86/include/asm/paravirt_types.h @@ -133,6 +133,12 @@ struct pv_mmu_ops { void (*flush_tlb_multi)(const struct cpumask *cpus, const struct flush_tlb_info *info); + /* + * Indicates whether flush_tlb_multi IPIs provide sufficient + * synchronization for GUP-fast when freeing or unsharing page tables. + */ + bool (*flush_tlb_multi_implies_ipi_broadcast)(void); + /* Hook for intercepting the destruction of an mm_struct. */ void (*exit_mmap)(struct mm_struct *mm); void (*notify_page_enc_status_changed)(unsigned long pfn, int npages, bool enc); diff --git a/arch/x86/include/asm/tlb.h b/arch/x86/include/asm/tlb.h index 866ea78ba156..3a7cdfdcea8e 100644 --- a/arch/x86/include/asm/tlb.h +++ b/arch/x86/include/asm/tlb.h @@ -5,10 +5,26 @@ #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 + if (pv_ops.mmu.flush_tlb_multi_implies_ipi_broadcast) + return pv_ops.mmu.flush_tlb_multi_implies_ipi_broadcast(); + + return false; +#else + return !cpu_feature_enabled(X86_FEATURE_INVLPGB); +#endif +} static inline void tlb_flush(struct mmu_gather *tlb) { @@ -20,7 +36,8 @@ 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) diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c index ab3e172dcc69..4eaa44800b39 100644 --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -60,6 +60,15 @@ void __init native_pv_lock_init(void) static_branch_enable(&virt_spin_lock_key); } +static bool native_flush_tlb_multi_implies_ipi_broadcast(void) +{ + /* Paravirt may use hypercalls that don't send real IPIs. */ + if (pv_ops.mmu.flush_tlb_multi != native_flush_tlb_multi) + return false; + + return !cpu_feature_enabled(X86_FEATURE_INVLPGB); +} + struct static_key paravirt_steal_enabled; struct static_key paravirt_steal_rq_enabled; @@ -173,6 +182,7 @@ struct paravirt_patch_template pv_ops = { .mmu.flush_tlb_kernel = native_flush_tlb_global, .mmu.flush_tlb_one_user = native_flush_tlb_one_user, .mmu.flush_tlb_multi = native_flush_tlb_multi, + .mmu.flush_tlb_multi_implies_ipi_broadcast = native_flush_tlb_multi_implies_ipi_broadcast, .mmu.exit_mmap = paravirt_nop, .mmu.notify_page_enc_status_changed = paravirt_nop, -- 2.49.0