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=-11.1 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_SANE_1 autolearn=unavailable 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 B73ECC433F5 for ; Fri, 3 Sep 2021 16:33:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9FB7560F12 for ; Fri, 3 Sep 2021 16:33:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350041AbhICQeg (ORCPT ); Fri, 3 Sep 2021 12:34:36 -0400 Received: from out30-42.freemail.mail.aliyun.com ([115.124.30.42]:56315 "EHLO out30-42.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235714AbhICQef (ORCPT ); Fri, 3 Sep 2021 12:34:35 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R671e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04423;MF=laijs@linux.alibaba.com;NM=1;PH=DS;RN=16;SR=0;TI=SMTPD_---0Un7a1Ii_1630686812; Received: from C02XQCBJJG5H.local(mailfrom:laijs@linux.alibaba.com fp:SMTPD_---0Un7a1Ii_1630686812) by smtp.aliyun-inc.com(127.0.0.1); Sat, 04 Sep 2021 00:33:33 +0800 Subject: Re: [PATCH 2/7] KVM: X86: Synchronize the shadow pagetable before link it To: Sean Christopherson Cc: Lai Jiangshan , linux-kernel@vger.kernel.org, Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Marcelo Tosatti , Avi Kivity , kvm@vger.kernel.org References: <20210824075524.3354-1-jiangshanlai@gmail.com> <20210824075524.3354-3-jiangshanlai@gmail.com> From: Lai Jiangshan Message-ID: Date: Sat, 4 Sep 2021 00:33:32 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/9/4 00:06, Sean Christopherson wrote: > -static void mmu_sync_children(struct kvm_vcpu *vcpu, > - struct kvm_mmu_page *parent) > +static int mmu_sync_children(struct kvm_vcpu *vcpu, > + struct kvm_mmu_page *parent, bool can_yield) > { > int i; > struct kvm_mmu_page *sp; > @@ -2050,7 +2050,15 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu, > flush |= kvm_sync_page(vcpu, sp, &invalid_list); > mmu_pages_clear_parents(&parents); > } > - if (need_resched() || rwlock_needbreak(&vcpu->kvm->mmu_lock)) { > + /* > + * Don't yield if there are fewer than unsync children > + * remaining, just finish up and get out. > + */ > + if (parent->unsync_children > SOME_ARBITRARY_THRESHOLD && > + (need_resched() || rwlock_needbreak(&vcpu->kvm->mmu_lock))) { > + if (!can_yield) > + return -EINTR; > + Another thought about this function. It is courtesy to break when rwlock_needbreak(), but the price is quite high, with remote flushing to interrupt several pCPUs. I think we can only break when need_resched().