From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2348DC433E0 for ; Thu, 2 Jul 2020 13:56:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 01DFE2088E for ; Thu, 2 Jul 2020 13:56:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729580AbgGBN4f (ORCPT ); Thu, 2 Jul 2020 09:56:35 -0400 Received: from szxga07-in.huawei.com ([45.249.212.35]:43088 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729472AbgGBN4W (ORCPT ); Thu, 2 Jul 2020 09:56:22 -0400 Received: from DGGEMS406-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id A246244A5C93F08B323C; Thu, 2 Jul 2020 21:56:15 +0800 (CST) Received: from DESKTOP-5IS4806.china.huawei.com (10.174.187.22) by DGGEMS406-HUB.china.huawei.com (10.3.19.206) with Microsoft SMTP Server id 14.3.487.0; Thu, 2 Jul 2020 21:56:09 +0800 From: Keqian Zhu To: , , , CC: Catalin Marinas , Marc Zyngier , James Morse , Will Deacon , "Suzuki K Poulose" , Steven Price , "Sean Christopherson" , Julien Thierry , Mark Brown , "Thomas Gleixner" , Andrew Morton , Alexios Zavras , , , , Keqian Zhu Subject: [PATCH v2 8/8] KVM: Omit dirty log sync in log clear if initially all set Date: Thu, 2 Jul 2020 21:55:56 +0800 Message-ID: <20200702135556.36896-9-zhukeqian1@huawei.com> X-Mailer: git-send-email 2.8.4.windows.1 In-Reply-To: <20200702135556.36896-1-zhukeqian1@huawei.com> References: <20200702135556.36896-1-zhukeqian1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.174.187.22] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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