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=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 46F0CC433E3 for ; Wed, 29 Jul 2020 01:00:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1B1CD20829 for ; Wed, 29 Jul 2020 01:00:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="mZiqc0JD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731034AbgG2BAf (ORCPT ); Tue, 28 Jul 2020 21:00:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48710 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729867AbgG2BAf (ORCPT ); Tue, 28 Jul 2020 21:00:35 -0400 Received: from mail-oi1-x241.google.com (mail-oi1-x241.google.com [IPv6:2607:f8b0:4864:20::241]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4690C061794; Tue, 28 Jul 2020 18:00:34 -0700 (PDT) Received: by mail-oi1-x241.google.com with SMTP id s144so9355860oie.3; Tue, 28 Jul 2020 18:00:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=JEhRoCG/lU8vWInqRMMLeNwglqgQ2Y0GNTOKaudATQY=; b=mZiqc0JDiQd0utiAotGRCqhWVhmGENNGKibl4o6mA0ZcZIh3vES80oGDaeiifU3nIj aHjPz2s4b1HQ3pir663dSykzgBJOL2Mo3Kg5X3sMY2aC1dpie6aBKg/MwfpKlOp7kohi YDTMTXh+KqhY0YQlQrcH0Ae/ETipl53oLxq6S9Imr9LW2Ded8MLHgzMv5/+ZBoagZSv6 3p13ohlK0wHL6MIkLg1D/2vHtPfSARjp1yAMjZafPyG5U+oMWtaAwrSy9Ntj1fRdTsTh YXaHSl/SOHGs2ywZAvgK8A90ysn/HBMvCQKyHdIbjUmiHU9wKGP+cVzxLTvBTFTp2brD 5pJw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=JEhRoCG/lU8vWInqRMMLeNwglqgQ2Y0GNTOKaudATQY=; b=Q5GILY+oGnEB84mgl7kTeMKosE6Oj9/Ci//AECCVo6gDlaC0g9x6Jy0Qx28S14XLRW t/Th9v5Q02JgFTOA2S1EHIysmK5IjKA1qAYp2GqkSkY0/4mI74dimd0ewlX4KH9xDbDF 3b/z2JtghY2UaNi09IOYDDjKONJrCQ3dVPsiEWvZwh3I7M6GVnG2av4Q8VAGWyiliI2E Jre/cT9rMgnhvuMTnnpwFqIz35ehvpUZie8g/y5JwjNDx8KnXNRjNO1OnRv5IKQUskle j0B5eJfcfuzxjpobNjEZBUd44B8NzMCaMMm/uiSsyxiypC+3en7DcpgaR9hvi2c6Flia ff8Q== X-Gm-Message-State: AOAM5328EUscnGd+OdCYr/ZLZ98KMHTK15RSKIf4jtfnd1epkVkH0UVD G4o+ODe6tuS4846NFaQwZoLtdaEaMY/OwYaXa5Y= X-Google-Smtp-Source: ABdhPJxWiV+84QJPgzngtJ4MAvLN1Yz/zUFEzfrUSVeUkCplsdRKVw/5aYHM0fGz2cuRgFgHt6mxOMS342usxvkB3ZQ= X-Received: by 2002:aca:5594:: with SMTP id j142mr5781232oib.33.1595984434290; Tue, 28 Jul 2020 18:00:34 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Wanpeng Li Date: Wed, 29 Jul 2020 09:00:22 +0800 Message-ID: Subject: Re: WARNING: suspicious RCU usage - while installing a VM on a CPU listed under nohz_full To: Nitesh Narayan Lal Cc: LKML , KVM list , Wanpeng Li , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Liran Alon , "frederic@kernel.org" , Thomas Gleixner , Juri Lelli Content-Type: text/plain; charset="UTF-8" Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, 28 Jul 2020 at 22:40, Nitesh Narayan Lal wrote: > > Hi, > > I have recently come across an RCU trace with the 5.8-rc7 kernel that has the > debug configs enabled while installing a VM on a CPU that is listed under > nohz_full. > > Based on some of the initial debugging, my impression is that the issue is > triggered because of the fastpath that is meant to optimize the writes to x2APIC > ICR that eventually leads to a virtual IPI in fixed delivery mode, is getting > invoked from the quiescent state. I still can reproduce this after removing the ipi/timer fastpath codes, anyway, I will have a look.