Synchronizing dirty log during log clear is useful only when the dirty bitmap of userspace contains dirty bits that memslot dirty bitmap does not contain, because we can sync new dirty bits to memslot dirty bitmap, then we can clear them by the way and avoid reporting them to userspace later. With dirty bitmap "initially all set" feature, the above situation will not appear if userspace logic is normal, so we can omit dirty log sync in log clear. This is valuable when dirty log sync is a high-cost operation, such as arm64 DBM. Signed-off-by: Keqian Zhu <zhukeqian1@xxxxxxxxxx> --- virt/kvm/kvm_main.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index a852af5c3214..3f9e51d52b7a 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1554,7 +1554,8 @@ static int kvm_clear_dirty_log_protect(struct kvm *kvm, (log->num_pages < memslot->npages - log->first_page && (log->num_pages & 63))) return -EINVAL; - kvm_arch_sync_dirty_log(kvm, memslot); + if (!kvm_dirty_log_manual_protect_and_init_set(kvm)) + kvm_arch_sync_dirty_log(kvm, memslot); flush = false; dirty_bitmap_buffer = kvm_second_dirty_bitmap(memslot); -- 2.19.1
