From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) (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 2607C7B for ; Mon, 6 Feb 2023 16:59:08 +0000 (UTC) Received: by mail-pj1-f73.google.com with SMTP id bk3-20020a17090b080300b0023098d62104so1846472pjb.7 for ; Mon, 06 Feb 2023 08:59:08 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=zzlWyFCqYcyGZzCULhoOstPX7ibhNXtVEONcSJrj+Jc=; b=HLLwmkjhmxTQyNCpagTXJVAaLKpNx2dLM8cXIXmhfJJrAbw7EzlGzw9IIkSRHpWfB8 yZwe45G0Sz7zaQstlj05xgJ7A0wYxWQa4KELG/b8qLQqrtwFJP2oJX0cxvA+xtaW0UJd OJlWkCjV9c/dHAjZUXQsrgcYU2kqrCPF9CzUpK7Sn9ppmsadmTh7vnl8e/ZvlfCTthdu nMcMxOxHEQcfRGFDT6iWKL7Bcm4DZdsFoIkUe3aZNVb5wrBqcOVwzuEEc1VCvy3h7Jny pZkPEo7joA2IZE0YvtDqIFuoiXw8UQkOf8jTTtJwvL+4pC1CCTVyx3X0PEqycNfnXSQj IdSg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; 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=zzlWyFCqYcyGZzCULhoOstPX7ibhNXtVEONcSJrj+Jc=; b=ieKyv9PaBYCXqSUBCeN0aT4g4IDgO5hVxhgDLO0bt1W47jXiNFujIm7VjBVZA0+rHu yzkaoE82rHZ+xgcJJrGE3EEwpEf+JgttF+lraLXAni+NtgYC8wWZoPPx5mzBJ0cXkJAk 3TscGfQezRspYKVKhA+kSYYxMede9CMprf/89jIw7xkpgKrZo8GxA+FVrVJt5yYp3HzL jBzPsHgOGEG044Lte30Bs7KZ9gPnRCUTAYFDUy9MMk37i1VVK3t4ZRUi4I2pvWB05vFj Nf/4oVcRtVis9zROWcD9CP1UGe05q7B1nwKDZfgQT7f5mSrKeG4P2WVwi64+kJYUg0+/ fV9A== X-Gm-Message-State: AO0yUKUrcjN+foSm6lXqLa31zx+I8Sh3uZVyb2HeJJvZLSXCM7/10ftD Xj1JntJqxCDHsqcq/+8NaHRav6zT2EDOyw== X-Google-Smtp-Source: AK7set9Sa9xH8cDy8qU28rf3Jsx4C/c70O1Yy7vzzH+DlFlqSo6pRcMhNRkBnC7LJI7dyxBps1pSsMsrhU2vDA== X-Received: from ricarkol4.c.googlers.com ([fda3:e722:ac3:cc00:20:ed76:c0a8:1248]) (user=ricarkol job=sendgmr) by 2002:a17:90a:2c05:b0:230:97d5:a224 with SMTP id m5-20020a17090a2c0500b0023097d5a224mr56108pjd.122.1675702747618; Mon, 06 Feb 2023 08:59:07 -0800 (PST) Date: Mon, 6 Feb 2023 16:58:47 +0000 In-Reply-To: <20230206165851.3106338-1-ricarkol@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20230206165851.3106338-1-ricarkol@google.com> X-Mailer: git-send-email 2.39.1.519.gcb327c4b5f-goog Message-ID: <20230206165851.3106338-9-ricarkol@google.com> Subject: [PATCH v2 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 | 2 ++ arch/arm64/kvm/arm.c | 22 ++++++++++++++++++++++ arch/arm64/kvm/mmu.c | 3 +++ include/uapi/linux/kvm.h | 1 + 5 files changed, 54 insertions(+) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 9807b05a1b57..a9332e331cce 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -8284,6 +8284,32 @@ 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 35a159d131b5..a69a815719cf 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -153,6 +153,8 @@ 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 + struct kvm_arch *arch; }; diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 9c5573bc4614..c80617ced599 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -101,6 +101,22 @@ 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; @@ -298,6 +314,12 @@ 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 812633a75e74..e2ada6588017 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -755,6 +755,9 @@ 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 55155e262646..02e05f7918e2 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1175,6 +1175,7 @@ struct kvm_ppc_resize_hpt { #define KVM_CAP_DIRTY_LOG_RING_ACQ_REL 223 #define KVM_CAP_S390_PROTECTED_ASYNC_DISABLE 224 #define KVM_CAP_DIRTY_LOG_RING_WITH_BITMAP 225 +#define KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE 226 #ifdef KVM_CAP_IRQ_ROUTING -- 2.39.1.519.gcb327c4b5f-goog