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=-18.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 16D53C433E0 for ; Wed, 10 Mar 2021 18:17:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DEBFD64FB2 for ; Wed, 10 Mar 2021 18:17:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233329AbhCJSQb (ORCPT ); Wed, 10 Mar 2021 13:16:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52650 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232802AbhCJSQJ (ORCPT ); Wed, 10 Mar 2021 13:16:09 -0500 Received: from mail-pj1-x1032.google.com (mail-pj1-x1032.google.com [IPv6:2607:f8b0:4864:20::1032]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5D170C061760 for ; Wed, 10 Mar 2021 10:16:09 -0800 (PST) Received: by mail-pj1-x1032.google.com with SMTP id x7-20020a17090a2b07b02900c0ea793940so7687873pjc.2 for ; Wed, 10 Mar 2021 10:16:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=hFGuoSs/aMUt+vuoT2J/eAJ6b5vWIpYR5D/n9ZHOWqc=; b=aNqu7VKy1TPjC3z/C75Zor9tecXd+bxXydROVEzPp1x66A0tlh89Rc/hakMzTZ7xGi W9QM1IsyQ3KcUoQktz6dSBl7MExGda2KHVRk6DGFqv0wP3iOPu4DUwnUxy0l+0fwCiaY CvfUg73/YcOhhYE4CxanRdJbVZe9ywxOlBSubR46nJfVS2aHbfEdgNZIOSr382nxM2qi R7VkIjKwiFP9L4PFJY5/FJq8ln5voZmsX9hY/c36f5fUt23IwRwty76Riz9df2BYrOmM AytY5zwrgdgWDpulLIHFVHVQIXLWer1CRk5pSgCb4G+s2EqPGqrY88/DLjvUg/D/OHdy S9QA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=hFGuoSs/aMUt+vuoT2J/eAJ6b5vWIpYR5D/n9ZHOWqc=; b=hildc2LC3ackQg+YkQTEPEP+LRf0aRjwTD1JY5dBOIdP/634We3jsVb4EdGzWV7mr0 VxACOiJAOsmD6X4/zyitlnHie8FrEzHWJejjl2p/4Zd4gr+FLz1Uu5RvE0nIEuzRTzOH sopbkOOLkZjZxV4orWeVit09/NyQH/WekYWj6WRZwAW1QVode4kmX1NXabqGEMpOETtJ Le2/ii9xnT3IJqafmKAM6FMUn+fno7dThPBJGmh8KFe31J/h8UhbGeox1EYVyxFujTxg n2c/dHetQ0AQ9/RMt/sWpcrW+PfaDd+r5sJHBQurF2VkXzNds8sPfbCzrsSOgeWXeiKt G9TQ== X-Gm-Message-State: AOAM530r719rfs8lysRKHVZE3ZROhpy9kdQqNdRZlr40i1cUFp4sQUGx dpRi/L1X6vRgC7wVPNuZF1ERAQ== X-Google-Smtp-Source: ABdhPJy3NKbaRwumU2/U9+KQHmV8ce7wBDcCVlJqxs7ogrpgwj28bGTCsOi1FLFxIfBdj/JOLxI3Cg== X-Received: by 2002:a17:902:ec84:b029:e5:bd05:4a98 with SMTP id x4-20020a170902ec84b02900e5bd054a98mr4158188plg.76.1615400168553; Wed, 10 Mar 2021 10:16:08 -0800 (PST) Received: from google.com ([2620:15c:f:10:e4dd:6c31:9463:f8da]) by smtp.gmail.com with ESMTPSA id mp19sm7390612pjb.2.2021.03.10.10.16.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Mar 2021 10:16:07 -0800 (PST) Date: Wed, 10 Mar 2021 10:16:00 -0800 From: Sean Christopherson To: Peter Zijlstra Cc: Ingo Molnar , Arnaldo Carvalho de Melo , Thomas Gleixner , Borislav Petkov , x86@kernel.org, Paolo Bonzini , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , "H. Peter Anvin" , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Like Xu , Dmitry Vyukov , syzbot+cce9ef2dd25246f815ee@syzkaller.appspotmail.com Subject: Re: [PATCH v2] x86/perf: Use RET0 as default for guest_get_msrs to handle "no PMU" case Message-ID: References: <20210309171019.1125243-1-seanjc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 10, 2021, Peter Zijlstra wrote: > On Tue, Mar 09, 2021 at 09:10:19AM -0800, Sean Christopherson wrote: > > > @@ -2024,9 +2021,6 @@ static int __init init_hw_perf_events(void) > > if (!x86_pmu.read) > > x86_pmu.read = _x86_pmu_read; > > > > - if (!x86_pmu.guest_get_msrs) > > - x86_pmu.guest_get_msrs = perf_guest_get_msrs_nop; > > I suspect I might've been over eager here and we're now in trouble when > *_pmu_init() clears x86_pmu.guest_get_msrs (like for instance on AMD). > > When that happens we need to restore __static_call_return0, otherwise > the following static_call_update() will patch in a NOP and RAX will be > garbage again. > > So I've taken the liberty to update the patch as below. Doh, I managed to forget about that between v1 and v2, too. Thanks much!