From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CE49734AA71 for ; Tue, 6 May 2025 00:49:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=96.67.55.147 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746492565; cv=none; b=rS93WZRSC1lMbC9YYuTusV/3SxN02f5CuOyVU2o8ZEcaxIxDD4oGKebSqeMXIG/TegmUCSo8tn3aUYY7p3P2I98EhC6Qe42wW2gJravO0kMjuEld3aXpMGQ/P9Zdh2K7pWfO/3bC9NX8SW2olEMByE7ocy8abCUyoIsLg01tpW8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746492565; c=relaxed/simple; bh=EV8op9KpgnmZmV/JxT0ECHLeduQDSWJev2uNMIO9cZo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dAF142/BIPFnL9rhO0flLbbZ8NydtWujzP7ea0AauoHv8KNSfoFScKWRDjNZKDK06AVTeILTMVArOLljSdrVUo89r/DnKN6d72snAzcwOyz7pH2xlec2N5P5bfrVuv6+NOKtuwMv6doQhYSxJ/WY6lVWYb/OE8ziPFBvGk1+J0g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=surriel.com; spf=pass smtp.mailfrom=shelob.surriel.com; arc=none smtp.client-ip=96.67.55.147 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=surriel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=shelob.surriel.com Received: from fangorn.home.surriel.com ([10.0.13.7]) by shelob.surriel.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.97.1) (envelope-from ) id 1uC6K6-000000000IF-40O7; Mon, 05 May 2025 20:38:14 -0400 From: Rik van Riel To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, x86@kernel.org, kernel-team@meta.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, Rik van Riel , Rik van Riel Subject: [RFC PATCH 9/9] x86/mm: userspace & pageout flushing using Intel RAR Date: Mon, 5 May 2025 20:37:47 -0400 Message-ID: <20250506003811.92405-10-riel@surriel.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250506003811.92405-1-riel@surriel.com> References: <20250506003811.92405-1-riel@surriel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: riel@surriel.com From: Rik van Riel Use Intel RAR to flush userspace mappings. Because RAR flushes are targeted using a cpu bitmap, the rules are a little bit different than for true broadcast TLB invalidation. For true broadcast TLB invalidation, like done with AMD INVLPGB, a global ASID always has up to date TLB entries on every CPU. The context switch code never has to flush the TLB when switching to a global ASID on any CPU with INVLPGB. For RAR, the TLB mappings for a global ASID are kept up to date only on CPUs within the mm_cpumask, which lazily follows the threads around the system. The context switch code does not need to flush the TLB if the CPU is in the mm_cpumask, and the PCID used stays the same. However, a CPU that falls outside of the mm_cpumask can have out of date TLB mappings for this task. When switching to that task on a CPU not in the mm_cpumask, the TLB does need to be flushed. Signed-off-by: Rik van Riel --- arch/x86/include/asm/tlbflush.h | 9 ++- arch/x86/mm/tlb.c | 119 +++++++++++++++++++++++++------- 2 files changed, 99 insertions(+), 29 deletions(-) diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h index e9b81876ebe4..1940d51f95a9 100644 --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -250,7 +250,8 @@ static inline u16 mm_global_asid(struct mm_struct *mm) { u16 asid; - if (!cpu_feature_enabled(X86_FEATURE_INVLPGB)) + if (!cpu_feature_enabled(X86_FEATURE_INVLPGB) && + !cpu_feature_enabled(X86_FEATURE_RAR)) return 0; asid = smp_load_acquire(&mm->context.global_asid); @@ -263,7 +264,8 @@ static inline u16 mm_global_asid(struct mm_struct *mm) static inline void mm_init_global_asid(struct mm_struct *mm) { - if (cpu_feature_enabled(X86_FEATURE_INVLPGB)) { + if (!cpu_feature_enabled(X86_FEATURE_INVLPGB) && + !cpu_feature_enabled(X86_FEATURE_RAR)) { mm->context.global_asid = 0; mm->context.asid_transition = false; } @@ -287,7 +289,8 @@ static inline void mm_clear_asid_transition(struct mm_struct *mm) static inline bool mm_in_asid_transition(struct mm_struct *mm) { - if (!cpu_feature_enabled(X86_FEATURE_INVLPGB)) + if (!cpu_feature_enabled(X86_FEATURE_INVLPGB) && + !cpu_feature_enabled(X86_FEATURE_RAR)) return false; return mm && READ_ONCE(mm->context.asid_transition); diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index a4f3941281b6..724359be3f97 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -235,9 +235,11 @@ static struct new_asid choose_new_asid(struct mm_struct *next, u64 next_tlb_gen) /* * TLB consistency for global ASIDs is maintained with hardware assisted - * remote TLB flushing. Global ASIDs are always up to date. + * remote TLB flushing. Global ASIDs are always up to date with INVLPGB, + * and up to date for CPUs in the mm_cpumask with RAR.. */ - if (cpu_feature_enabled(X86_FEATURE_INVLPGB)) { + if (cpu_feature_enabled(X86_FEATURE_INVLPGB) || + cpu_feature_enabled(X86_FEATURE_RAR)) { u16 global_asid = mm_global_asid(next); if (global_asid) { @@ -300,7 +302,14 @@ static void reset_global_asid_space(void) { lockdep_assert_held(&global_asid_lock); - invlpgb_flush_all_nonglobals(); + /* + * The global flush ensures that a freshly allocated global ASID + * has no entries in any TLB, and can be used immediately. + * With Intel RAR, the TLB may still need to be flushed at context + * switch time when dealing with a CPU that was not in the mm_cpumask + * for the process, and may have missed flushes along the way. + */ + flush_tlb_all(); /* * The TLB flush above makes it safe to re-use the previously @@ -377,7 +386,7 @@ static void use_global_asid(struct mm_struct *mm) { u16 asid; - guard(raw_spinlock_irqsave)(&global_asid_lock); + guard(raw_spinlock)(&global_asid_lock); /* This process is already using broadcast TLB invalidation. */ if (mm_global_asid(mm)) @@ -403,13 +412,14 @@ static void use_global_asid(struct mm_struct *mm) void mm_free_global_asid(struct mm_struct *mm) { - if (!cpu_feature_enabled(X86_FEATURE_INVLPGB)) + if (!cpu_feature_enabled(X86_FEATURE_INVLPGB) && + !cpu_feature_enabled(X86_FEATURE_RAR)) return; if (!mm_global_asid(mm)) return; - guard(raw_spinlock_irqsave)(&global_asid_lock); + guard(raw_spinlock)(&global_asid_lock); /* The global ASID can be re-used only after flush at wrap-around. */ #ifdef CONFIG_BROADCAST_TLB_FLUSH @@ -427,7 +437,8 @@ static bool mm_needs_global_asid(struct mm_struct *mm, u16 asid) { u16 global_asid = mm_global_asid(mm); - if (!cpu_feature_enabled(X86_FEATURE_INVLPGB)) + if (!cpu_feature_enabled(X86_FEATURE_INVLPGB) && + !cpu_feature_enabled(X86_FEATURE_RAR)) return false; /* Process is transitioning to a global ASID */ @@ -445,7 +456,8 @@ static bool mm_needs_global_asid(struct mm_struct *mm, u16 asid) */ static void consider_global_asid(struct mm_struct *mm) { - if (!cpu_feature_enabled(X86_FEATURE_INVLPGB)) + if (!cpu_feature_enabled(X86_FEATURE_INVLPGB) && + !cpu_feature_enabled(X86_FEATURE_RAR)) return; /* Check every once in a while. */ @@ -499,7 +511,7 @@ static void finish_asid_transition(struct flush_tlb_info *info) mm_clear_asid_transition(mm); } -static void broadcast_tlb_flush(struct flush_tlb_info *info) +static void invlpgb_tlb_flush(struct flush_tlb_info *info) { bool pmd = info->stride_shift == PMD_SHIFT; unsigned long asid = mm_global_asid(info->mm); @@ -865,13 +877,6 @@ void switch_mm_irqs_off(struct mm_struct *unused, struct mm_struct *next, goto reload_tlb; } - /* - * Broadcast TLB invalidation keeps this ASID up to date - * all the time. - */ - if (is_global_asid(prev_asid)) - return; - /* * If the CPU is not in lazy TLB mode, we are just switching * from one thread in a process to another thread in the same @@ -880,6 +885,15 @@ void switch_mm_irqs_off(struct mm_struct *unused, struct mm_struct *next, if (!was_lazy) return; + /* + * Broadcast TLB invalidation keeps this ASID up to date + * all the time with AMD INVLPGB. Intel RAR may need a TLB + * flush if the CPU was in lazy TLB mode.. + */ + if (cpu_feature_enabled(X86_FEATURE_INVLPGB) && + is_global_asid(prev_asid)) + return; + /* * Read the tlb_gen to check whether a flush is needed. * If the TLB is up to date, just use it. @@ -912,20 +926,27 @@ void switch_mm_irqs_off(struct mm_struct *unused, struct mm_struct *next, this_cpu_write(cpu_tlbstate.loaded_mm, LOADED_MM_SWITCHING); barrier(); - /* Start receiving IPIs and then read tlb_gen (and LAM below) */ - if (next != &init_mm && !cpumask_test_cpu(cpu, mm_cpumask(next))) - cpumask_set_cpu(cpu, mm_cpumask(next)); + /* A TLB flush started during a context switch is harmless. */ next_tlb_gen = atomic64_read(&next->context.tlb_gen); ns = choose_new_asid(next, next_tlb_gen); + + /* Start receiving IPIs and RAR invalidations */ + if (next != &init_mm && !cpumask_test_cpu(cpu, mm_cpumask(next))) { + cpumask_set_cpu(cpu, mm_cpumask(next)); + /* CPUs outside mm_cpumask may be out of date. */ + if (cpu_feature_enabled(X86_FEATURE_RAR)) + ns.need_flush = true; + } } reload_tlb: new_lam = mm_lam_cr3_mask(next); if (ns.need_flush) { - VM_WARN_ON_ONCE(is_global_asid(ns.asid)); - this_cpu_write(cpu_tlbstate.ctxs[ns.asid].ctx_id, next->context.ctx_id); - this_cpu_write(cpu_tlbstate.ctxs[ns.asid].tlb_gen, next_tlb_gen); + if (is_dyn_asid(ns.asid)) { + this_cpu_write(cpu_tlbstate.ctxs[ns.asid].ctx_id, next->context.ctx_id); + this_cpu_write(cpu_tlbstate.ctxs[ns.asid].tlb_gen, next_tlb_gen); + } load_new_mm_cr3(next->pgd, ns.asid, new_lam, true); trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL); @@ -1142,8 +1163,12 @@ static void flush_tlb_func(void *info) loaded_mm_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid); } - /* Broadcast ASIDs are always kept up to date with INVLPGB. */ - if (is_global_asid(loaded_mm_asid)) + /* + * Broadcast ASIDs are always kept up to date with INVLPGB; with + * Intel RAR IPI based flushes are used periodically to trim the + * mm_cpumask. Make sure those flushes are processed here. + */ + if (cpu_feature_enabled(X86_FEATURE_INVLPGB) && is_global_asid(loaded_mm_asid)) return; VM_WARN_ON(this_cpu_read(cpu_tlbstate.ctxs[loaded_mm_asid].ctx_id) != @@ -1363,6 +1388,33 @@ static DEFINE_PER_CPU_SHARED_ALIGNED(struct flush_tlb_info, flush_tlb_info); static DEFINE_PER_CPU(unsigned int, flush_tlb_info_idx); #endif +static void rar_tlb_flush(struct flush_tlb_info *info) +{ + unsigned long asid = mm_global_asid(info->mm); + u16 pcid = kern_pcid(asid); + + /* Flush the remote CPUs. */ + smp_call_rar_many(mm_cpumask(info->mm), pcid, info->start, info->end); + if (cpu_feature_enabled(X86_FEATURE_PTI)) + smp_call_rar_many(mm_cpumask(info->mm), user_pcid(asid), info->start, info->end); + + /* Flush the local TLB, if needed. */ + if (cpumask_test_cpu(smp_processor_id(), mm_cpumask(info->mm))) { + lockdep_assert_irqs_enabled(); + local_irq_disable(); + flush_tlb_func(info); + local_irq_enable(); + } +} + +static void broadcast_tlb_flush(struct flush_tlb_info *info) +{ + if (cpu_feature_enabled(X86_FEATURE_INVLPGB)) + invlpgb_tlb_flush(info); + else /* Intel RAR */ + rar_tlb_flush(info); +} + static struct flush_tlb_info *get_flush_tlb_info(struct mm_struct *mm, unsigned long start, unsigned long end, unsigned int stride_shift, bool freed_tables, @@ -1423,15 +1475,22 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start, info = get_flush_tlb_info(mm, start, end, stride_shift, freed_tables, new_tlb_gen); + /* + * IPIs and RAR can be targeted to a cpumask. Periodically trim that + * mm_cpumask by sending TLB flush IPIs, even when most TLB flushes + * are done with RAR. + */ + if (!cpu_feature_enabled(X86_FEATURE_INVLPGB) || !mm_global_asid(mm)) + info->trim_cpumask = should_trim_cpumask(mm); + /* * flush_tlb_multi() is not optimized for the common case in which only * a local TLB flush is needed. Optimize this use-case by calling * flush_tlb_func_local() directly in this case. */ - if (mm_global_asid(mm)) { + if (mm_global_asid(mm) && !info->trim_cpumask) { broadcast_tlb_flush(info); } else if (cpumask_any_but(mm_cpumask(mm), cpu) < nr_cpu_ids) { - info->trim_cpumask = should_trim_cpumask(mm); flush_tlb_multi(mm_cpumask(mm), info); consider_global_asid(mm); } else if (mm == this_cpu_read(cpu_tlbstate.loaded_mm)) { @@ -1742,6 +1801,14 @@ void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch) if (cpu_feature_enabled(X86_FEATURE_INVLPGB) && batch->unmapped_pages) { invlpgb_flush_all_nonglobals(); batch->unmapped_pages = false; + } else if (cpu_feature_enabled(X86_FEATURE_RAR) && cpumask_any(&batch->cpumask) < nr_cpu_ids) { + rar_full_flush(&batch->cpumask); + if (cpumask_test_cpu(cpu, &batch->cpumask)) { + lockdep_assert_irqs_enabled(); + local_irq_disable(); + invpcid_flush_all_nonglobals(); + local_irq_enable(); + } } else if (cpumask_any_but(&batch->cpumask, cpu) < nr_cpu_ids) { flush_tlb_multi(&batch->cpumask, info); } else if (cpumask_test_cpu(cpu, &batch->cpumask)) { -- 2.49.0