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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B30C8C433F5 for ; Tue, 19 Oct 2021 16:59:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 931DC6113B for ; Tue, 19 Oct 2021 16:59:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234192AbhJSRCC (ORCPT ); Tue, 19 Oct 2021 13:02:02 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:26284 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229774AbhJSRCB (ORCPT ); Tue, 19 Oct 2021 13:02:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1634662787; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=yRL6nOjnZK6b2+TcoLEmu3K5pdW1k8luCFoncQ412YQ=; b=M7AgYvtHT7Trjh2iYCaOz3s2onFx9kKS3fUUdhe6KxCBQnNNL7xjnrHoxOo7Owup0zKbrj XnzVBeFnigkjcaA32CiRD/fJ0WMgXtk6i8hP+E579LsHESWroSqtkkDQa78FhIZbeJnTNb NFDNKvDOaYvP9EZdxo9CkQW7yTXzqxg= Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-62-W2J9e-49N_iZ62zhZxVLRQ-1; Tue, 19 Oct 2021 12:59:46 -0400 X-MC-Unique: W2J9e-49N_iZ62zhZxVLRQ-1 Received: by mail-ed1-f72.google.com with SMTP id a3-20020a50da43000000b003dca31dcfc2so1811004edk.14 for ; Tue, 19 Oct 2021 09:59:46 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=yRL6nOjnZK6b2+TcoLEmu3K5pdW1k8luCFoncQ412YQ=; b=w4sij0jUyBvhIo8wcl13RFvPcXzQFWYRwvHRkmUBPPP9Rr+tukhkuI1WX6TEA9htr1 kHM2G84ak7QFsFyfiV1ANkrF+38RFp+56Mh2h6AkHIQ4v6Py88r4zjgZmsQwFahcV2c7 P32hensc5k7c6MWmeGo8FqUNPMHs1OKTQ5ac5u0Fu9G704ZYydzNQajVJEC0RxipQJU9 Sx9sNMxnwcMAW99iJzIIKUtx2gy7rj1xhBIFcKybl0561ZC8ROvMlUc9dpu9x7NSjAuX JMnglvbZKLc9A8hZVHqez+3LdADGZKzGrb94qxQqj7mOC5W9YE2TOr4g6M8f71SoOOc7 51oQ== X-Gm-Message-State: AOAM530pVl1YpMt90EJDAGabOveu0hO/Zjp8enx9KSi0tSrq/4QBtLCT Jqe7hG8ZQdNhy09hshP7ONl8yAx+CN13xICozNbhiRprcza/7MRVrY4R6HBfMNg3LptV95xpHWl P/6kSzgD9GeJSNHijSr003JKm X-Received: by 2002:a17:907:1006:: with SMTP id ox6mr39717453ejb.146.1634662785168; Tue, 19 Oct 2021 09:59:45 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzqI0DI3vHAHu36Mp/AOE/8zmn2909YkRm8xBz5go4Ysf4/It0HRvh0G4456fXpfkQ2JUaAcw== X-Received: by 2002:a17:907:1006:: with SMTP id ox6mr39717415ejb.146.1634662784936; Tue, 19 Oct 2021 09:59:44 -0700 (PDT) Received: from ?IPV6:2001:b07:6468:f312:8e02:b072:96b1:56d0? ([2001:b07:6468:f312:8e02:b072:96b1:56d0]) by smtp.gmail.com with ESMTPSA id l19sm12897787edb.65.2021.10.19.09.59.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 19 Oct 2021 09:59:44 -0700 (PDT) Message-ID: <24e67e43-c50c-7e0f-305a-c7f6129f8d70@redhat.com> Date: Tue, 19 Oct 2021 18:59:43 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.1.0 Subject: Re: [PATCH v3 3/3] KVM: vCPU kick tax cut for running vCPU Content-Language: en-US To: Wanpeng Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel References: <1634631160-67276-1-git-send-email-wanpengli@tencent.com> <1634631160-67276-3-git-send-email-wanpengli@tencent.com> From: Paolo Bonzini In-Reply-To: <1634631160-67276-3-git-send-email-wanpengli@tencent.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/10/21 10:12, Wanpeng Li wrote: > - if (kvm_vcpu_wake_up(vcpu)) > - return; > + me = get_cpu(); > + > + if (rcuwait_active(kvm_arch_vcpu_get_wait(vcpu)) && kvm_vcpu_wake_up(vcpu)) > + goto out; This is racy. You are basically doing the same check that rcuwait_wake_up does, but without the memory barrier before. Also here: > + if (vcpu == __this_cpu_read(kvm_running_vcpu)) { > + WARN_ON_ONCE(vcpu->mode == IN_GUEST_MODE); it's better to do if (vcpu == ... && !WARN_ON_ONCE(vcpu->mode == IN_GUEST_MODE)) goto out; so that if the bug happens you do get a smp_send_reschedule() and fail safely. Paolo > + goto out; > + }