aboutsummaryrefslogtreecommitdiff
path: root/virt
diff options
context:
space:
mode:
authorJay Zhou <jianjay.zhou@huawei.com>2020-02-27 09:32:27 +0800
committerPaolo Bonzini <pbonzini@redhat.com>2020-03-16 17:57:37 +0100
commit3c9bd4006bfc2dccda1823db61b3f470ef91cfaa (patch)
tree914a3fee54c7c102dfa8b6fd289cd1d18b6db19c /virt
parent0be44352071dc87a4f9bf879642b1d44876971d9 (diff)
downloadlinux-3c9bd4006bfc2dccda1823db61b3f470ef91cfaa.tar.gz
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 <jianjay.zhou@huawei.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/kvm_main.c24
1 files changed, 17 insertions, 7 deletions
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);