From patchwork Thu Jan 17 13:55:31 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhuang Yanying X-Patchwork-Id: 10768291 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id AB30813B4 for ; Thu, 17 Jan 2019 14:00:41 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9ACAD2FF7C for ; Thu, 17 Jan 2019 14:00:41 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8F5742FF83; Thu, 17 Jan 2019 14:00:41 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2F0AC2FF7C for ; Thu, 17 Jan 2019 14:00:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727182AbfAQOAk (ORCPT ); Thu, 17 Jan 2019 09:00:40 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:2188 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727429AbfAQOAj (ORCPT ); Thu, 17 Jan 2019 09:00:39 -0500 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 9800F2660A04C23BC4D6; Thu, 17 Jan 2019 22:00:34 +0800 (CST) Received: from localhost (10.177.21.2) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.408.0; Thu, 17 Jan 2019 22:00:27 +0800 From: Zhuangyanying To: , , CC: , , , , Zhuang Yanying Subject: [PATCH 4/4] KVM: MMU: fast cleanup D bit based on fast write protect Date: Thu, 17 Jan 2019 13:55:31 +0000 Message-ID: <1547733331-16140-5-git-send-email-ann.zhuangyanying@huawei.com> X-Mailer: git-send-email 2.6.4.windows.1 In-Reply-To: <1547733331-16140-1-git-send-email-ann.zhuangyanying@huawei.com> References: <1547733331-16140-1-git-send-email-ann.zhuangyanying@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.177.21.2] X-CFilter-Loop: Reflected Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Zhuang Yanying When live-migration with large-memory guests, vcpu may hang for a long time while starting migration, such as 9s for 2T (linux-5.0.0-rc2+qemu-3.1.0). The reason is memory_global_dirty_log_start() taking too long, and the vcpu is waiting for BQL. The page-by-page D bit clearup is the main time consumption. I think that the idea of "KVM: MMU: fast write protect" by xiaoguangrong, especially the function kvm_mmu_write_protect_all_pages(), is very helpful. After a little modifcation, on his patch, can solve this problem, 9s to 0.5s. At the beginning of live migration, write protection is only applied to the top-level SPTE. Then the write from vm trigger the EPT violation, with for_each_shadow_entry write protection is performed at dirct_map. Finally the Dirty bit of the target page(at level 1 page table) is cleared, and the dirty page tracking is started. Of coure, the page where GPA is located is marked dirty when mmu_set_spte. A similar implementation on xen, just emt instead of write protection. Signed-off-by: Zhuang Yanying --- arch/x86/kvm/mmu.c | 8 +++++--- arch/x86/kvm/vmx/vmx.c | 3 +-- 2 files changed, 6 insertions(+), 5 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 047b897..a18bcc0 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3257,7 +3257,10 @@ static bool mmu_load_shadow_page(struct kvm *kvm, struct kvm_mmu_page *sp) break; if (is_last_spte(spte, sp->role.level)) { - flush |= spte_write_protect(sptep, false); + if (sp->role.level == PT_PAGE_TABLE_LEVEL) + flush |= spte_clear_dirty(sptep); + else + flush |= spte_write_protect(sptep, false); continue; } @@ -6114,7 +6117,6 @@ void kvm_mmu_write_protect_all_pages(struct kvm *kvm, bool write_protect) { u64 wp_all_indicator, kvm_wp_all_gen; - mutex_lock(&kvm->slots_lock); wp_all_indicator = get_write_protect_all_indicator(kvm); kvm_wp_all_gen = get_write_protect_all_gen(wp_all_indicator); @@ -6134,8 +6136,8 @@ void kvm_mmu_write_protect_all_pages(struct kvm *kvm, bool write_protect) */ if (write_protect) kvm_reload_remote_mmus(kvm); - mutex_unlock(&kvm->slots_lock); } +EXPORT_SYMBOL_GPL(kvm_mmu_write_protect_all_pages); static unsigned long mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index f6915f1..5236a07 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -7180,8 +7180,7 @@ 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); - kvm_mmu_slot_largepage_remove_write_access(kvm, slot); + kvm_mmu_write_protect_all_pages(kvm, true); } static void vmx_slot_disable_log_dirty(struct kvm *kvm,