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Mon, 13 Jan 2025 09:06:32 -0800 (PST) MIME-Version: 1.0 References: <20250112155453.1104139-1-riel@surriel.com> <20250112155453.1104139-11-riel@surriel.com> In-Reply-To: <20250112155453.1104139-11-riel@surriel.com> From: Jann Horn Date: Mon, 13 Jan 2025 18:05:56 +0100 X-Gm-Features: AbW1kvaDYARxIdg5DC1Y9qTSh0yp9OW5RrjlvOkK7DBVV7no-vPEDTvBDTUwm4I Message-ID: Subject: Re: [PATCH v4 10/12] x86,tlb: do targeted broadcast flushing from tlbbatch code To: Rik van Riel Cc: x86@kernel.org, linux-kernel@vger.kernel.org, bp@alien8.de, peterz@infradead.org, dave.hansen@linux.intel.com, zhengqi.arch@bytedance.com, nadav.amit@gmail.com, thomas.lendacky@amd.com, kernel-team@meta.com, linux-mm@kvack.org, akpm@linux-foundation.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: C24D4140016 X-Rspamd-Server: rspam12 X-Stat-Signature: wb15wxii7ek5k3qdoxc11du87ykzhkcc X-Rspam-User: X-HE-Tag: 1736787994-188123 X-HE-Meta: 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 Pg6appbj XXmGPTuA3Rxc0pNwjThhDGMAK0GLaGnO3QwTUVk7qBCm3WM6jlV7KzfWIH2CQdIPC8fJxd5WVHrlIUDCu4/GIGH/YtAq9A5CwTdPD3kbKZqffSmNOlKcPVQflY5biZuNxTUYBOkJWQUX1nrI279nX6hHtag3XwOu2o3WhIxe3hz28sDgSjg4vIjsQGmaPQzIm4DhfntpJvrfHtIbDY7T0YK6vT4H8KvOxuhysrl+7nKC5jb2cJZ5qBc5DGXapDUpcbXllOFSb/3Kcmo9AFK7l+oXnPHRuE9TFcDKRqUtL/FDdq3kfEYIgD1OapPxh6fcDVT7isNf/GDlZDLA= X-Bogosity: Ham, tests=bogofilter, spamicity=0.006004, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, Jan 12, 2025 at 4:55=E2=80=AFPM Rik van Riel wro= te: > Instead of doing a system-wide TLB flush from arch_tlbbatch_flush, > queue up asynchronous, targeted flushes from arch_tlbbatch_add_pending. > > This also allows us to avoid adding the CPUs of processes using broadcast > flushing to the batch->cpumask, and will hopefully further reduce TLB > flushing from the reclaim and compaction paths. [...] > diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c > index 80375ef186d5..532911fbb12a 100644 > --- a/arch/x86/mm/tlb.c > +++ b/arch/x86/mm/tlb.c > @@ -1658,9 +1658,7 @@ void arch_tlbbatch_flush(struct arch_tlbflush_unmap= _batch *batch) > * a local TLB flush is needed. Optimize this use-case by calling > * flush_tlb_func_local() directly in this case. > */ > - if (cpu_feature_enabled(X86_FEATURE_INVLPGB)) { > - invlpgb_flush_all_nonglobals(); > - } else if (cpumask_any_but(&batch->cpumask, cpu) < nr_cpu_ids) { > + if (cpumask_any_but(&batch->cpumask, cpu) < nr_cpu_ids) { > flush_tlb_multi(&batch->cpumask, info); > } else if (cpumask_test_cpu(cpu, &batch->cpumask)) { > lockdep_assert_irqs_enabled(); > @@ -1669,12 +1667,49 @@ void arch_tlbbatch_flush(struct arch_tlbflush_unm= ap_batch *batch) > local_irq_enable(); > } > > + /* > + * If we issued (asynchronous) INVLPGB flushes, wait for them her= e. > + * The cpumask above contains only CPUs that were running tasks > + * not using broadcast TLB flushing. > + */ > + if (cpu_feature_enabled(X86_FEATURE_INVLPGB) && batch->used_invlp= gb) { > + tlbsync(); > + migrate_enable(); > + batch->used_invlpgb =3D false; > + } > + > cpumask_clear(&batch->cpumask); > > put_flush_tlb_info(); > put_cpu(); > } > > +void arch_tlbbatch_add_pending(struct arch_tlbflush_unmap_batch *batch, > + struct mm_struct *mm, > + unsigned long uaddr) > +{ > + if (static_cpu_has(X86_FEATURE_INVLPGB) && mm_global_asid(mm)) { > + u16 asid =3D mm_global_asid(mm); > + /* > + * Queue up an asynchronous invalidation. The correspondi= ng > + * TLBSYNC is done in arch_tlbbatch_flush(), and must be = done > + * on the same CPU. > + */ > + if (!batch->used_invlpgb) { > + batch->used_invlpgb =3D true; > + migrate_disable(); > + } > + invlpgb_flush_user_nr_nosync(kern_pcid(asid), uaddr, 1, f= alse); > + /* Do any CPUs supporting INVLPGB need PTI? */ > + if (static_cpu_has(X86_FEATURE_PTI)) > + invlpgb_flush_user_nr_nosync(user_pcid(asid), uad= dr, 1, false); > + } else { > + inc_mm_tlb_gen(mm); > + cpumask_or(&batch->cpumask, &batch->cpumask, mm_cpumask(m= m)); > + } > + mmu_notifier_arch_invalidate_secondary_tlbs(mm, 0, -1UL); > +} How does this work if the MM is currently transitioning to a global ASID? Should the "mm_global_asid(mm)" check maybe be replaced with something that checks if the MM has fully transitioned to a global ASID, so that we keep using the classic path if there might be holdout CPUs?