From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 09E9CC11D2F for ; Mon, 24 Feb 2020 17:05:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C5A9C20838 for ; Mon, 24 Feb 2020 17:05:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="YHFndL2b" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727426AbgBXRFr (ORCPT ); Mon, 24 Feb 2020 12:05:47 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:53483 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727259AbgBXRFq (ORCPT ); Mon, 24 Feb 2020 12:05:46 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582563945; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=APSdrhGv5raplzY6i75KWcyOo+Dgfm4GE5GDcIoP7hg=; b=YHFndL2brV1KIoi2gdYwchm6zejN/FX7ARpabi483I4DrSjPyXu0i6QgGHeiTh6SpuUZq0 d/bCOoO4M0QUH8Heh22vYJIcLLwitgLA6lQHzTvTBMhvSusqg5CQYG8f7UPVEaGZ8scgFQ t+iM2BG3oOqkFKxAkt6B4EX3N/m4TdA= Received: from mail-qk1-f197.google.com (mail-qk1-f197.google.com [209.85.222.197]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-432-cF6tQdBqPsadpUfOXqU9tQ-1; Mon, 24 Feb 2020 12:05:42 -0500 X-MC-Unique: cF6tQdBqPsadpUfOXqU9tQ-1 Received: by mail-qk1-f197.google.com with SMTP id o22so11337144qko.2 for ; Mon, 24 Feb 2020 09:05:42 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=APSdrhGv5raplzY6i75KWcyOo+Dgfm4GE5GDcIoP7hg=; b=hTJAhMkOTDNmwciy0b68RYf50k1DwZHfUr7fLHdX1Xj72cDwZAIqd48KooaT4ZgA4m p+tOhupA1KSYqfdO+2i8pQ3feQryJmGI2yvNS6/YHVqRG8b28iLbefk+NC0kD5fLUNJy IZiCaMPJxkkrr6k9f2fzc78PF9lqjVRqTphBqNIthmCjNdRKkWXjzj8wvGNnCHETcdBU e43PCyEfvFgsKTl5AaF+Z0g7qSZpMJdtSc6ygmUooWc21XT8bP2RvZmX+DV7BGU2FPOW 91toAr3i6lq+F1fFL29PPMDwdBTRhiOI2NslGwHuV6+uQQZ9JwyVduwcGKhFCm1iaxgq viMg== X-Gm-Message-State: APjAAAVqa1HWaeoKioou2MhSDMY6ehRnhHPzd3N454pBw8xFhw9v/g7N MqI1aMFuaxMgdUkyIGVEvW47GWqAEl8U1iqb9WRNcuMsdMin3I0Mj8TMvwfPNrAL6KNPHfY0qq1 vnTiyXpiRLt5P X-Received: by 2002:a37:a00e:: with SMTP id j14mr9635223qke.464.1582563941537; Mon, 24 Feb 2020 09:05:41 -0800 (PST) X-Google-Smtp-Source: APXvYqzOhco545pi1Mc1TmwoFaZrnSVHVQG6JDOG70N9dneMzGk6ijHALjxEfTtSJQ1GJohn0W5o9A== X-Received: by 2002:a37:a00e:: with SMTP id j14mr9635173qke.464.1582563941060; Mon, 24 Feb 2020 09:05:41 -0800 (PST) Received: from xz-x1 ([104.156.64.75]) by smtp.gmail.com with ESMTPSA id g62sm6058811qkd.25.2020.02.24.09.05.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Feb 2020 09:05:39 -0800 (PST) Date: Mon, 24 Feb 2020 12:05:38 -0500 From: Peter Xu To: Jay Zhou Cc: kvm@vger.kernel.org, pbonzini@redhat.com, sean.j.christopherson@intel.com, wangxinxin.wang@huawei.com, weidong.huang@huawei.com, liu.jinsong@huawei.com Subject: Re: [PATCH v3] KVM: x86: enable dirty log gradually in small chunks Message-ID: <20200224170538.GH37727@xz-x1> References: <20200224032558.2728-1-jianjay.zhou@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200224032558.2728-1-jianjay.zhou@huawei.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Feb 24, 2020 at 11:25:58AM +0800, Jay Zhou wrote: > It could take kvm->mmu_lock for an extended period of time when > enabling dirty log for the first time. The main cost is to clear > all the D-bits of last level SPTEs. This situation can benefit from > manual dirty log protect as well, which can reduce the mmu_lock > time taken. The sequence is like this: > > 1. Initialize all the bits of the dirty bitmap to 1 when enabling > dirty log for the first time > 2. Only write protect the huge pages > 3. KVM_GET_DIRTY_LOG returns the dirty bitmap info > 4. KVM_CLEAR_DIRTY_LOG will clear D-bit for each of the leaf level > SPTEs gradually in small chunks > > Under the Intel(R) Xeon(R) Gold 6152 CPU @ 2.10GHz environment, > I did some tests with a 128G windows VM and counted the time taken > of memory_global_dirty_log_start, here is the numbers: > > VM Size Before After optimization > 128G 460ms 10ms > > Signed-off-by: Jay Zhou > --- > v3: > * add kvm_manual_dirty_log_init_set helper, add testcase on top and > keep old behavior for KVM_MEM_READONLY [Peter] > * tweak logic at enabling KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 [Sean, Peter] > > v2: > * add new bit to KVM_ENABLE_CAP for KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 [Paolo] > * support non-PML path [Peter] > * delete the unnecessary ifdef and make the initialization of bitmap > more clear [Sean] > * document the new bits and tweak the testcase > > Documentation/virt/kvm/api.rst | 16 +++++++++++++--- > arch/x86/include/asm/kvm_host.h | 3 ++- > arch/x86/kvm/mmu/mmu.c | 7 ++++--- > arch/x86/kvm/vmx/vmx.c | 3 ++- > arch/x86/kvm/x86.c | 18 +++++++++++++++--- > include/linux/kvm_host.h | 9 ++++++++- > virt/kvm/kvm_main.c | 30 +++++++++++++++++++++++------- > 7 files changed, 67 insertions(+), 19 deletions(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index 97a72a5..807fcd7 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -5704,10 +5704,20 @@ and injected exceptions. > :Architectures: x86, arm, arm64, mips > :Parameters: args[0] whether feature should be enabled or not > > -With this capability enabled, KVM_GET_DIRTY_LOG will not automatically > -clear and write-protect all pages that are returned as dirty. > +Valid flags are:: > + > + #define KVM_DIRTY_LOG_MANUAL_PROTECT2 (1 << 0) > + #define KVM_DIRTY_LOG_INITIALLY_SET (1 << 1) I think I mis-read previously on the old version so my comment was misleading. If this is the sub-capability within KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2, then I don't think we need to have the ending "2" any more. How about: KVM_MANUAL_PROTECT_ENABLE KVM_MANUAL_PROTECT_INIT_ALL_SET ? Sorry about that. > + > +With KVM_DIRTY_LOG_MANUAL_PROTECT2 set, KVM_GET_DIRTY_LOG will not > +automatically clear and write-protect all pages that are returned as dirty. > Rather, userspace will have to do this operation separately using > KVM_CLEAR_DIRTY_LOG. > +With KVM_DIRTY_LOG_INITIALLY_SET set, all the bits of the dirty bitmap > +will be initialized to 1 when created, dirty logging will be enabled > +gradually in small chunks using KVM_CLEAR_DIRTY_LOG. However, the > +KVM_DIRTY_LOG_INITIALLY_SET depends on KVM_DIRTY_LOG_MANUAL_PROTECT2, > +it can not be set individually and supports x86 only for now. > > At the cost of a slightly more complicated operation, this provides better > scalability and responsiveness for two reasons. First, > @@ -5716,7 +5726,7 @@ than requiring to sync a full memslot; this ensures that KVM does not > take spinlocks for an extended period of time. Second, in some cases a > large amount of time can pass between a call to KVM_GET_DIRTY_LOG and > userspace actually using the data in the page. Pages can be modified > -during this time, which is inefficint for both the guest and userspace: > +during this time, which is inefficient for both the guest and userspace: > the guest will incur a higher penalty due to write protection faults, > while userspace can see false reports of dirty pages. Manual reprotection > helps reducing this time, improving guest performance and reducing the > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 40a0c0f..a90630c 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -1312,7 +1312,8 @@ void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask, > > void kvm_mmu_reset_context(struct kvm_vcpu *vcpu); > void kvm_mmu_slot_remove_write_access(struct kvm *kvm, > - struct kvm_memory_slot *memslot); > + struct kvm_memory_slot *memslot, > + int start_level); > void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm, > const struct kvm_memory_slot *memslot); > void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm, > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 87e9ba2..a4e70eb 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -5860,13 +5860,14 @@ static bool slot_rmap_write_protect(struct kvm *kvm, > } > > void kvm_mmu_slot_remove_write_access(struct kvm *kvm, > - struct kvm_memory_slot *memslot) > + struct kvm_memory_slot *memslot, > + int start_level) > { > bool flush; > > spin_lock(&kvm->mmu_lock); > - flush = slot_handle_all_level(kvm, memslot, slot_rmap_write_protect, > - false); > + flush = slot_handle_level(kvm, memslot, slot_rmap_write_protect, > + start_level, PT_MAX_HUGEPAGE_LEVEL, false); > spin_unlock(&kvm->mmu_lock); > > /* > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 3be25ec..0deb8c3 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -7201,7 +7201,8 @@ static void vmx_sched_in(struct kvm_vcpu *vcpu, int cpu) > static void vmx_slot_enable_log_dirty(struct kvm *kvm, > struct kvm_memory_slot *slot) > { > - kvm_mmu_slot_leaf_clear_dirty(kvm, slot); > + if (!kvm_manual_dirty_log_init_set(kvm)) > + kvm_mmu_slot_leaf_clear_dirty(kvm, slot); > kvm_mmu_slot_largepage_remove_write_access(kvm, slot); > } > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index fb5d64e..f816940 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -9956,7 +9956,7 @@ static void kvm_mmu_slot_apply_flags(struct kvm *kvm, > { > /* Still write protect RO slot */ > if (new->flags & KVM_MEM_READONLY) { > - kvm_mmu_slot_remove_write_access(kvm, new); > + kvm_mmu_slot_remove_write_access(kvm, new, PT_PAGE_TABLE_LEVEL); > return; > } > > @@ -9993,8 +9993,20 @@ static void kvm_mmu_slot_apply_flags(struct kvm *kvm, > if (new->flags & KVM_MEM_LOG_DIRTY_PAGES) { > if (kvm_x86_ops->slot_enable_log_dirty) > kvm_x86_ops->slot_enable_log_dirty(kvm, new); > - else > - kvm_mmu_slot_remove_write_access(kvm, new); > + else { > + int level = kvm_manual_dirty_log_init_set(kvm) ? > + PT_DIRECTORY_LEVEL : PT_PAGE_TABLE_LEVEL; > + > + /* > + * If we're with initial-all-set, we don't need > + * to write protect any small page because > + * they're reported as dirty already. However > + * we still need to write-protect huge pages > + * so that the page split can happen lazily on > + * the first write to the huge page. > + */ > + kvm_mmu_slot_remove_write_access(kvm, new, level); > + } > } else { > if (kvm_x86_ops->slot_disable_log_dirty) > kvm_x86_ops->slot_disable_log_dirty(kvm, new); > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index e89eb67..80ada94 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -360,6 +360,13 @@ static inline unsigned long *kvm_second_dirty_bitmap(struct kvm_memory_slot *mem > return memslot->dirty_bitmap + len / sizeof(*memslot->dirty_bitmap); > } > > +#define KVM_DIRTY_LOG_MANUAL_PROTECT2 (1 << 0) > +#define KVM_DIRTY_LOG_INITIALLY_SET (1 << 1) > +#define KVM_DIRTY_LOG_MANUAL_CAPS (KVM_DIRTY_LOG_MANUAL_PROTECT2 | \ > + KVM_DIRTY_LOG_INITIALLY_SET) > + > +bool kvm_manual_dirty_log_init_set(struct kvm *kvm); > + > struct kvm_s390_adapter_int { > u64 ind_addr; > u64 summary_addr; > @@ -493,7 +500,7 @@ struct kvm { > #endif > long tlbs_dirty; > struct list_head devices; > - bool manual_dirty_log_protect; > + u64 manual_dirty_log_protect; > struct dentry *debugfs_dentry; > struct kvm_stat_data **debugfs_stat_data; > struct srcu_struct srcu; > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 70f03ce..0ffb804 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -858,11 +858,17 @@ static int kvm_vm_release(struct inode *inode, struct file *filp) > return 0; > } > > +bool kvm_manual_dirty_log_init_set(struct kvm *kvm) > +{ > + return kvm->manual_dirty_log_protect & KVM_DIRTY_LOG_INITIALLY_SET; > +} Nit: this can be put into kvm_host.h as inlined. > +EXPORT_SYMBOL_GPL(kvm_manual_dirty_log_init_set); > + > /* > * Allocation size is twice as large as the actual dirty bitmap size. > * See x86's kvm_vm_ioctl_get_dirty_log() why this is needed. > */ > -static int kvm_create_dirty_bitmap(struct kvm_memory_slot *memslot) > +static int kvm_alloc_dirty_bitmap(struct kvm_memory_slot *memslot) > { > unsigned long dirty_bytes = 2 * kvm_dirty_bitmap_bytes(memslot); > > @@ -1094,8 +1100,11 @@ int __kvm_set_memory_region(struct kvm *kvm, > > /* Allocate page dirty bitmap if needed */ > if ((new.flags & KVM_MEM_LOG_DIRTY_PAGES) && !new.dirty_bitmap) { > - if (kvm_create_dirty_bitmap(&new) < 0) > + if (kvm_alloc_dirty_bitmap(&new)) > goto out_free; > + > + if (kvm_manual_dirty_log_init_set(kvm)) > + bitmap_set(new.dirty_bitmap, 0, new.npages); > } > > slots = kvzalloc(sizeof(struct kvm_memslots), GFP_KERNEL_ACCOUNT); > @@ -3310,9 +3319,6 @@ static long kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) > case KVM_CAP_IOEVENTFD_ANY_LENGTH: > case KVM_CAP_CHECK_EXTENSION_VM: > case KVM_CAP_ENABLE_CAP_VM: > -#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT > - case KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2: > -#endif > return 1; > #ifdef CONFIG_KVM_MMIO > case KVM_CAP_COALESCED_MMIO: > @@ -3320,6 +3326,10 @@ static long kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) > case KVM_CAP_COALESCED_PIO: > return 1; > #endif > +#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT > + case KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2: > + return KVM_DIRTY_LOG_MANUAL_CAPS; We probably can only return the new feature bit when with CONFIG_X86? > +#endif > #ifdef CONFIG_HAVE_KVM_IRQ_ROUTING > case KVM_CAP_IRQ_ROUTING: > return KVM_MAX_IRQ_ROUTES; > @@ -3347,11 +3357,17 @@ static int kvm_vm_ioctl_enable_cap_generic(struct kvm *kvm, > { > switch (cap->cap) { > #ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT > - case KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2: > - if (cap->flags || (cap->args[0] & ~1)) > + case KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2: { > + u64 allowed_options = KVM_DIRTY_LOG_MANUAL_PROTECT2; > + > + if (cap->args[0] & KVM_DIRTY_LOG_MANUAL_PROTECT2) > + allowed_options |= KVM_DIRTY_LOG_INITIALLY_SET; Same here to check against CONFIG_X86? > + > + if (cap->flags || (cap->args[0] & ~allowed_options)) > return -EINVAL; > kvm->manual_dirty_log_protect = cap->args[0]; > return 0; > + } > #endif > default: > return kvm_vm_ioctl_enable_cap(kvm, cap); > -- > 1.8.3.1 > > Thanks, -- Peter Xu