From patchwork Mon Feb 24 03:25:58 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Zhoujian (jay)" X-Patchwork-Id: 11399201 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5F07492A for ; Mon, 24 Feb 2020 03:26:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2FACF2071C for ; Mon, 24 Feb 2020 03:26:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727168AbgBXD0b (ORCPT ); Sun, 23 Feb 2020 22:26:31 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:11102 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727156AbgBXD0a (ORCPT ); Sun, 23 Feb 2020 22:26:30 -0500 Received: from DGGEMS405-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 9D51EF99E702EC59DF86; Mon, 24 Feb 2020 11:26:24 +0800 (CST) Received: from localhost (10.173.228.206) by DGGEMS405-HUB.china.huawei.com (10.3.19.205) with Microsoft SMTP Server id 14.3.439.0; Mon, 24 Feb 2020 11:26:16 +0800 From: Jay Zhou To: CC: , , , , , , Subject: [PATCH v3] KVM: x86: enable dirty log gradually in small chunks Date: Mon, 24 Feb 2020 11:25:58 +0800 Message-ID: <20200224032558.2728-1-jianjay.zhou@huawei.com> X-Mailer: git-send-email 2.14.1.windows.1 MIME-Version: 1.0 X-Originating-IP: [10.173.228.206] X-CFilter-Loop: Reflected Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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) + +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; +} +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; +#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; + + 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);