From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BA5AD36E for ; Tue, 7 Mar 2023 03:46:11 +0000 (UTC) Received: by mail-pj1-f74.google.com with SMTP id m9-20020a17090a7f8900b0023769205928so7404223pjl.6 for ; Mon, 06 Mar 2023 19:46:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1678160771; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=gvJNj0mQeIAybmV+sHqcHxeWw8+9xyXfDJ8xf/pLTCA=; b=KuFR4KTgeSooNzN/+zGbVnqYq4wq4kyTAhwmrHbGurV9+8hMkG2Qc8H09cvvDcqzGg j/IhFToTxYiAmo9iNXaSMdkUN2ylaxTvtcDiqK1cz3ReHAa/BXICOcoEB/nNoZXnmO83 fA4ikyiPQ6H04H0L3HO2zkDhxVnZLuXMeyTlhbpa96jztGxSaIUxSLgRyxLwkANp6p8L MDDxBGPTa0u7fv3JEfFSYSuBU6MtxwgbdmLsuS2e7KQ9y4T4vqq+u5IppD4sU2Zqelud Iib8XjYPWsrMBWHKGQGSKZ9OpEvD3mqpeRtMdBhtaOVQJp+9izt59WrnPkhKhmT4hFUd veTQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678160771; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=gvJNj0mQeIAybmV+sHqcHxeWw8+9xyXfDJ8xf/pLTCA=; b=nQZlkKcUqcGmETgOj3nurxF8WH6LsVYwxnwXSwuoEG7KoLDDbjhyN8LOSu6rjrSmhK KcS9S2lwrPSNy1oLNE1zIrINqJA55ZwoO4vn51JA/QxWo2yh0i8IKj/M490H2qMs1jI8 EUgRXVd3Tsh02YF5njQc6l5krS5l0GLh2J1OJPGqTbBwwAXybe3FFwyAAkZs8/8uYpc4 qatPOgKNAIKcBLecmQOS3x1zVj5IYAqMIkIEJr9Vp87C8PqzULuerSt2Um54AwqJsioN imJBhiamkzPeijHJ8cWy6bovyvszf1OqpVdT361W2FrF7J0cbCV1sc02qW1UT5ZJhHZf TJCA== X-Gm-Message-State: AO0yUKXODAW75PNSCHNvCoKY6THgyZXnR/6fF1w6p6PQz2uGgtF4YjmY M8E3Js/XSvQ7U0kz8pzBnrcFrhWFB7UQbw== X-Google-Smtp-Source: AK7set9SV3zCXNwHWNNDJ8yWRWTV0zHQlV0Jsaxr1Bj4VcYs8eaYZCCL4+YdsU8YvpCLjZQiLrjrMF14QfO+CQ== X-Received: from ricarkol4.c.googlers.com ([fda3:e722:ac3:cc00:20:ed76:c0a8:1248]) (user=ricarkol job=sendgmr) by 2002:a17:902:ef95:b0:19b:8be:33dc with SMTP id iz21-20020a170902ef9500b0019b08be33dcmr5059517plb.6.1678160771101; Mon, 06 Mar 2023 19:46:11 -0800 (PST) Date: Tue, 7 Mar 2023 03:45:51 +0000 In-Reply-To: <20230307034555.39733-1-ricarkol@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20230307034555.39733-1-ricarkol@google.com> X-Mailer: git-send-email 2.40.0.rc0.216.gc4246ad0f0-goog Message-ID: <20230307034555.39733-9-ricarkol@google.com> Subject: [PATCH v6 08/12] KVM: arm64: Add KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE From: Ricardo Koller To: pbonzini@redhat.com, maz@kernel.org, oupton@google.com, yuzenghui@huawei.com, dmatlack@google.com Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev, qperret@google.com, catalin.marinas@arm.com, andrew.jones@linux.dev, seanjc@google.com, alexandru.elisei@arm.com, suzuki.poulose@arm.com, eric.auger@redhat.com, gshan@redhat.com, reijiw@google.com, rananta@google.com, bgardon@google.com, ricarkol@gmail.com, Ricardo Koller , Oliver Upton Content-Type: text/plain; charset="UTF-8" Add a capability for userspace to specify the eager split chunk size. The chunk size specifies how many pages to break at a time, using a single allocation. Bigger the chunk size, more pages need to be allocated ahead of time. Suggested-by: Oliver Upton Signed-off-by: Ricardo Koller --- Documentation/virt/kvm/api.rst | 26 ++++++++++++++++++++++++++ arch/arm64/include/asm/kvm_host.h | 19 +++++++++++++++++++ arch/arm64/kvm/arm.c | 22 ++++++++++++++++++++++ arch/arm64/kvm/mmu.c | 3 +++ include/uapi/linux/kvm.h | 1 + 5 files changed, 71 insertions(+) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 62de0768d6aa..872dae7cfbe0 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -8380,6 +8380,32 @@ structure. When getting the Modified Change Topology Report value, the attr->addr must point to a byte where the value will be stored or retrieved from. +8.40 KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE +--------------------------------------- + +:Capability: KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE +:Architectures: arm64 +:Type: vm +:Parameters: arg[0] is the new chunk size. +:Returns: 0 on success, -EINVAL if any memslot has been created. + +This capability sets the chunk size used in Eager Page Splitting. + +Eager Page Splitting improves the performance of dirty-logging (used +in live migrations) when guest memory is backed by huge-pages. This +optimization is enabled by default on arm64. It avoids splitting +huge-pages (into PAGE_SIZE pages) on fault, by doing it eagerly when +enabling dirty logging (with the KVM_MEM_LOG_DIRTY_PAGES flag for a +memory region), or when using KVM_CLEAR_DIRTY_LOG. + +The chunk size specifies how many pages to break at a time, using a +single allocation for each chunk. Bigger the chunk size, more pages +need to be allocated ahead of time. A good heuristic is to pick the +size of the huge-pages as the chunk size. + +If the chunk size (arg[0]) is zero, then no eager page splitting is +performed. The default value PMD size (e.g., 2M when PAGE_SIZE is 4K). + 9. Known KVM API problems ========================= diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index a1892a8f6032..b7755d0cbd4d 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -158,6 +158,25 @@ struct kvm_s2_mmu { /* The last vcpu id that ran on each physical CPU */ int __percpu *last_vcpu_ran; +#define KVM_ARM_EAGER_SPLIT_CHUNK_SIZE_DEFAULT PMD_SIZE + /* + * Memory cache used to split + * KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE worth of huge pages. It + * is used to allocate stage2 page tables while splitting huge + * pages. Note that the choice of EAGER_PAGE_SPLIT_CHUNK_SIZE + * influences both the capacity of the split page cache, and + * how often KVM reschedules. Be wary of raising CHUNK_SIZE + * too high. + * + * A good heuristic to pick CHUNK_SIZE is that it should be + * the size of the huge-pages backing guest memory. If not + * known, the PMD size (usually 2M) is a good guess. + * + * Protected by kvm->slots_lock. + */ + struct kvm_mmu_memory_cache split_page_cache; + uint64_t split_page_chunk_size; + struct kvm_arch *arch; }; diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 3bd732eaf087..3468fee223ae 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -91,6 +91,22 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, r = 0; set_bit(KVM_ARCH_FLAG_SYSTEM_SUSPEND_ENABLED, &kvm->arch.flags); break; + case KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE: + mutex_lock(&kvm->lock); + mutex_lock(&kvm->slots_lock); + /* + * To keep things simple, allow changing the chunk + * size only if there are no memslots created. + */ + if (!kvm_are_all_memslots_empty(kvm)) { + r = -EINVAL; + } else { + r = 0; + kvm->arch.mmu.split_page_chunk_size = cap->args[0]; + } + mutex_unlock(&kvm->slots_lock); + mutex_unlock(&kvm->lock); + break; default: r = -EINVAL; break; @@ -288,6 +304,12 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_ARM_PTRAUTH_GENERIC: r = system_has_full_ptr_auth(); break; + case KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE: + if (kvm) + r = kvm->arch.mmu.split_page_chunk_size; + else + r = KVM_ARM_EAGER_SPLIT_CHUNK_SIZE_DEFAULT; + break; default: r = 0; } diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index a2800e5c4271..898985b09321 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -756,6 +756,9 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t for_each_possible_cpu(cpu) *per_cpu_ptr(mmu->last_vcpu_ran, cpu) = -1; + mmu->split_page_cache.gfp_zero = __GFP_ZERO; + mmu->split_page_chunk_size = KVM_ARM_EAGER_SPLIT_CHUNK_SIZE_DEFAULT; + mmu->pgt = pgt; mmu->pgd_phys = __pa(pgt->pgd); return 0; diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index d77aef872a0a..af43acdc7901 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1184,6 +1184,7 @@ struct kvm_ppc_resize_hpt { #define KVM_CAP_S390_PROTECTED_ASYNC_DISABLE 224 #define KVM_CAP_DIRTY_LOG_RING_WITH_BITMAP 225 #define KVM_CAP_PMU_EVENT_MASKED_EVENTS 226 +#define KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE 227 #ifdef KVM_CAP_IRQ_ROUTING -- 2.40.0.rc0.216.gc4246ad0f0-goog