From 3c9bd4006bfc2dccda1823db61b3f470ef91cfaa Mon Sep 17 00:00:00 2001 From: Jay Zhou Date: Thu, 27 Feb 2020 09:32:27 +0800 Subject: KVM: x86: enable dirty log gradually in small chunks 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 Signed-off-by: Paolo Bonzini --- virt/kvm/kvm_main.c | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) (limited to 'virt') diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 26ccb6c0a461..699ff9b35c88 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -858,7 +858,7 @@ static int kvm_vm_release(struct inode *inode, struct file *filp) * Allocation size is twice as large as the actual dirty bitmap size. * See 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); @@ -1288,9 +1288,12 @@ int __kvm_set_memory_region(struct kvm *kvm, if (!(new.flags & KVM_MEM_LOG_DIRTY_PAGES)) new.dirty_bitmap = NULL; else if (!new.dirty_bitmap) { - r = kvm_create_dirty_bitmap(&new); + r = kvm_alloc_dirty_bitmap(&new); if (r) return r; + + if (kvm_dirty_log_manual_protect_and_init_set(kvm)) + bitmap_set(new.dirty_bitmap, 0, new.npages); } r = kvm_set_memslot(kvm, mem, &old, &new, as_id, change); @@ -3529,9 +3532,6 @@ 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: @@ -3539,6 +3539,10 @@ 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; @@ -3566,11 +3570,17 @@ 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_PROTECT_ENABLE; + + if (cap->args[0] & KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE) + allowed_options = KVM_DIRTY_LOG_MANUAL_CAPS; + + 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); -- cgit v1.2.3