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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A8229C4332F for ; Fri, 23 Dec 2022 02:15:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236004AbiLWCPu (ORCPT ); Thu, 22 Dec 2022 21:15:50 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58874 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235957AbiLWCP1 (ORCPT ); Thu, 22 Dec 2022 21:15:27 -0500 Received: from mail-pg1-x52e.google.com (mail-pg1-x52e.google.com [IPv6:2607:f8b0:4864:20::52e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8CDDC2657E; Thu, 22 Dec 2022 18:13:11 -0800 (PST) Received: by mail-pg1-x52e.google.com with SMTP id 78so2472765pgb.8; Thu, 22 Dec 2022 18:13:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=Fv83sILRpdPDju6R9bwpPHliUEsFsFUyc/dbMvww/eY=; b=L9N/WyPIseuqFdRkaF/UjdKRVnKl/YPV+cw9Zzr/bVwG7U+pnmawxLFt6oC4GYfZl5 5OTDOGp5Sv6kBdUxd4zxlFyP0arPQ1gP1iQU5C3tWa3iC/oFbAWDR8THSvihtlXzxR9w LPQU/52bv8JGe0H6X2Moysv/YJbnTsvmT2xphrTAerxfXuserbALUfdIZ08y3wEsFwYZ yD5hJUFCnZfk4w7OvL65caDFsKACCRa80ochQKr+zTLvHwu/ULv3pA+2kJ0dfLa88UDW SbVrWG6UAI5PBoy54k4PQ01awA3bLU1mfFLVinQKwFNe0/FwCSzjd05cBHVXyRwaLGoy reBA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Fv83sILRpdPDju6R9bwpPHliUEsFsFUyc/dbMvww/eY=; b=AVWzl2qoUmQjZax4qiTkwc/a9MzjlfUmHlSFKwCJ+ZQfl7l7MIVMLK/PmrCDHQfb+r UKrdre3I4eWx810d0JNh4bCBwKE6H6Ez8Lp8INPqYdS4hezqRSJO+JZjN3CljoNNj5VN OtOhQpeZ/PcJIQ96nuQGOHnQlRZB6BCIAG2IkaEse9riFLAG5xOFU9eUmMBJqVLZXt9t o6/TyQsEjkNO8IKfF3hYpfK09WUNVziv1Gm1yBAmjsiy9la+fMi+bZt0fFHU1mXlXR0x WdgMLsjnzWIBbep4jZ3Et0IyNOMY9B8rLBSm4M87QfLSgtHIyV9N5WbfsagdrAJgNtIU fr9Q== X-Gm-Message-State: AFqh2kqxPv3OqwQm6AUgadtEbPhpVyEMfksBy/LlOPW5Nq4a1/m0JlJm i/cbFMOSjIkTYYUrjlagaXQ= X-Google-Smtp-Source: AMrXdXuHlQaLGVeaQ6tC4E3lw5u7txRz+nS3SToycQ+iwH6FlwJZoMDxhM2TmgcpkbwagmAjZ9/MzQ== X-Received: by 2002:aa7:9794:0:b0:577:f836:6bcb with SMTP id o20-20020aa79794000000b00577f8366bcbmr9694825pfp.29.1671761581818; Thu, 22 Dec 2022 18:13:01 -0800 (PST) Received: from [192.168.255.10] ([103.7.29.32]) by smtp.gmail.com with ESMTPSA id p66-20020a622945000000b00561dcfa700asm1326991pfp.107.2022.12.22.18.12.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Dec 2022 18:13:01 -0800 (PST) Message-ID: Date: Fri, 23 Dec 2022 10:12:52 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [PATCH v2 01/15] perf/x86/lbr: Simplify the exposure check for the LBR_INFO registers Content-Language: en-US To: Peter Zijlstra , Sean Christopherson Cc: kan.liang@linux.intel.com, wei.w.wang@intel.com, Andi Kleen , "Paolo Bonzini - Distinguished Engineer (kernel-recipes.org) (KVM HoF)" , Jim Mattson , kvm list , "linux-kernel@vger.kernel.org" , Yang Weijiang References: <20221125040604.5051-1-weijiang.yang@intel.com> <20221125040604.5051-2-weijiang.yang@intel.com> <449b561a-7053-8994-bcfe-581c0abb8d85@gmail.com> From: Like Xu In-Reply-To: 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 23/12/2022 1:41 am, Sean Christopherson wrote: > On Thu, Dec 22, 2022, Like Xu wrote: >> Hi Peter, would you help apply this one in your tip/perf tree, >> as it doesn't seem to be closely tied to the KVM changes. Thanks. >> >> On 25/11/2022 12:05 pm, Yang Weijiang wrote: >>> From: Like Xu >>> >>> The x86_pmu.lbr_info is 0 unless explicitly initialized, so there's >>> no point checking x86_pmu.intel_cap.lbr_format. >>> >>> Cc: Peter Zijlstra >>> Reviewed-by: Kan Liang >>> Reviewed-by: Andi Kleen >>> Signed-off-by: Like Xu >>> Signed-off-by: Yang Weijiang >>> --- >>> arch/x86/events/intel/lbr.c | 4 +--- >>> 1 file changed, 1 insertion(+), 3 deletions(-) >>> >>> diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c >>> index 4dbde69c423b..e7caabfa1377 100644 >>> --- a/arch/x86/events/intel/lbr.c >>> +++ b/arch/x86/events/intel/lbr.c >>> @@ -1606,12 +1606,10 @@ void __init intel_pmu_arch_lbr_init(void) >>> */ >>> void x86_perf_get_lbr(struct x86_pmu_lbr *lbr) >>> { >>> - int lbr_fmt = x86_pmu.intel_cap.lbr_format; >>> - >>> lbr->nr = x86_pmu.lbr_nr; >>> lbr->from = x86_pmu.lbr_from; >>> lbr->to = x86_pmu.lbr_to; >>> - lbr->info = (lbr_fmt == LBR_FORMAT_INFO) ? x86_pmu.lbr_info : 0; >>> + lbr->info = x86_pmu.lbr_info; > > This stable-worthy a bug fix, no? E.g. won't the existing code misreport lbr->info > if the format is LBR_FORMAT_INFO2? Sure, we need "Cc: stable@vger.kernel.org" in order not to lose misprediction and cycles information on the LBR_FORMAT_INFO2 platforms like Goldmont plus. > >>> } >>> EXPORT_SYMBOL_GPL(x86_perf_get_lbr);