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Mon, 29 Dec 2025 06:54:55 -0800 (PST) Received: from EBJ9932692.tcent.cn ([103.88.46.167]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-34e70dbcb6esm31557603a91.9.2025.12.29.06.54.47 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 29 Dec 2025 06:54:55 -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 2/3] x86/mm: implement redundant IPI elimination for page table operations Date: Mon, 29 Dec 2025 22:52:44 +0800 Message-ID: <20251229145245.85452-3-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: rspam12 X-Rspamd-Queue-Id: D5911180016 X-Stat-Signature: hfgqrinhdega9bn8in3mbrs5bwsjfmy8 X-Rspam-User: X-HE-Tag: 1767020096-903222 X-HE-Meta: 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 TmFr8RNZ FgkOw1xoZlYr4N/jaV8AP/hBdDZ/OjIvd17mDtHWw11ACnf7g2bmPdRpVeMovzbR/ysW1xgMewZzWI800C/2q3kyVmTCgXbAiPx0uhvhBV+OQlTVbXpXeLBUuHI/WVvVeFhCuvPgT7xszOcby6aqUb1NM5nabWtrvSr391abtuguKOKRTUN63E46MxA== 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