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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 38556C83013 for ; Wed, 2 Jul 2025 05:44:42 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uWqFX-0004Uv-Nv; Wed, 02 Jul 2025 01:43:15 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uWqFS-0004UM-4k for qemu-devel@nongnu.org; Wed, 02 Jul 2025 01:43:10 -0400 Received: from mgamail.intel.com ([192.198.163.16]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uWqFH-0008VU-Rl for qemu-devel@nongnu.org; Wed, 02 Jul 2025 01:43:07 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1751434979; x=1782970979; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=JJu1pmmEn3alemdY/GcZx7/cDMvAq6dvoCyNi0CgS2Y=; b=F2qyyJew4WiGvu8dJgyqTDTWE0qsxqpkTvro9sS+N7cc9kahIJnbqEAe 2MK/aj75qlFaw3ARx/KObZ9yJIXtTV8RMi092UO2K/h9Z5JyMW19XRQKF 2JqD2ySaTuZyqXjQ5trl9Ys6n71QTzpFRdCrDqCCe9/y2RFGQZ7YpFC0l mWKioQ+CidIZ4Zipfwk8ghCaJ5iS9LAvccDkdejN71p/c4GGq4DVMney3 8WoH9aFhBnPFq3L+C6Aqg7CS9+67TZwE+7gXOFsRGMPOr1gbmLQcij4cV O+vZ2QWoyu3b3oKqpMJkGmKE1H+wP9AAqgM0Zz1TOg/Hc0yYESHc4VlJe Q==; X-CSE-ConnectionGUID: i03PfyhyRJi5eflQFLOehg== X-CSE-MsgGUID: 8eOf8c9TR3uV5EA2fsVD9Q== X-IronPort-AV: E=McAfee;i="6800,10657,11481"; a="41347898" X-IronPort-AV: E=Sophos;i="6.16,281,1744095600"; d="scan'208";a="41347898" Received: from orviesa006.jf.intel.com ([10.64.159.146]) by fmvoesa110.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Jul 2025 22:42:49 -0700 X-CSE-ConnectionGUID: H3MZBqqZQZ2uSfRfKb7nHQ== X-CSE-MsgGUID: QqYDOrwuSy+jl9lKGS8glw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.16,281,1744095600"; d="scan'208";a="153441060" Received: from dapengmi-mobl1.ccr.corp.intel.com (HELO [10.124.240.80]) ([10.124.240.80]) by orviesa006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Jul 2025 22:42:44 -0700 Message-ID: Date: Wed, 2 Jul 2025 13:42:41 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 9/9] target/i386/kvm: don't stop Intel PMU counters To: Dongli Zhang , qemu-devel@nongnu.org, kvm@vger.kernel.org Cc: pbonzini@redhat.com, zhao1.liu@intel.com, mtosatti@redhat.com, sandipan.das@amd.com, babu.moger@amd.com, likexu@tencent.com, like.xu.linux@gmail.com, groug@kaod.org, khorenko@virtuozzo.com, alexander.ivanov@virtuozzo.com, den@virtuozzo.com, davydov-max@yandex-team.ru, xiaoyao.li@intel.com, joe.jin@oracle.com, ewanhai-oc@zhaoxin.com, ewanhai@zhaoxin.com References: <20250624074421.40429-1-dongli.zhang@oracle.com> <20250624074421.40429-10-dongli.zhang@oracle.com> Content-Language: en-US From: "Mi, Dapeng" In-Reply-To: <20250624074421.40429-10-dongli.zhang@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Received-SPF: none client-ip=192.198.163.16; envelope-from=dapeng1.mi@linux.intel.com; helo=mgamail.intel.com X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 6/24/2025 3:43 PM, Dongli Zhang wrote: > PMU MSRs are set by QEMU only at levels >= KVM_PUT_RESET_STATE, > excluding runtime. Therefore, updating these MSRs without stopping events > should be acceptable. > > In addition, KVM creates kernel perf events with host mode excluded > (exclude_host = 1). While the events remain active, they don't increment > the counter during QEMU vCPU userspace mode. > > Finally, The kvm_put_msrs() sets the MSRs using KVM_SET_MSRS. The x86 KVM > processes these MSRs one by one in a loop, only saving the config and > triggering the KVM_REQ_PMU request. This approach does not immediately stop > the event before updating PMC. This approach is true since Linux kernel > commit 68fb4757e867 ("KVM: x86/pmu: Defer reprogram_counter() to > kvm_pmu_handle_event"), that is, v6.2. > > No Fixed tag is going to be added for the commit 0d89436786b0 ("kvm: > migrate vPMU state"), because this isn't a bugfix. > > Signed-off-by: Dongli Zhang > Reviewed-by: Zhao Liu > --- > Changed since v3: > - Re-order reasons in commit messages. > - Mention KVM's commit 68fb4757e867 (v6.2). > - Keep Zhao's review as there isn't code change. > > target/i386/kvm/kvm.c | 9 --------- > 1 file changed, 9 deletions(-) > > diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c > index 4bbdf996ef..207de21404 100644 > --- a/target/i386/kvm/kvm.c > +++ b/target/i386/kvm/kvm.c > @@ -4186,13 +4186,6 @@ static int kvm_put_msrs(X86CPU *cpu, int level) > } > > if ((IS_INTEL_CPU(env) || IS_ZHAOXIN_CPU(env)) && pmu_version > 0) { > - if (pmu_version > 1) { > - /* Stop the counter. */ > - kvm_msr_entry_add(cpu, MSR_CORE_PERF_FIXED_CTR_CTRL, 0); > - kvm_msr_entry_add(cpu, MSR_CORE_PERF_GLOBAL_CTRL, 0); > - } > - > - /* Set the counter values. */ > for (i = 0; i < num_pmu_fixed_counters; i++) { > kvm_msr_entry_add(cpu, MSR_CORE_PERF_FIXED_CTR0 + i, > env->msr_fixed_counters[i]); > @@ -4208,8 +4201,6 @@ static int kvm_put_msrs(X86CPU *cpu, int level) > env->msr_global_status); > kvm_msr_entry_add(cpu, MSR_CORE_PERF_GLOBAL_OVF_CTRL, > env->msr_global_ovf_ctrl); > - > - /* Now start the PMU. */ > kvm_msr_entry_add(cpu, MSR_CORE_PERF_FIXED_CTR_CTRL, > env->msr_fixed_ctr_ctrl); > kvm_msr_entry_add(cpu, MSR_CORE_PERF_GLOBAL_CTRL, Reviewed-by: Dapeng Mi