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 3EB1AC19F32 for ; Wed, 5 Mar 2025 07:41:31 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tpjNB-0000Sq-OG; Wed, 05 Mar 2025 02:40:58 -0500 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 1tpjN9-0000Sb-D6 for qemu-devel@nongnu.org; Wed, 05 Mar 2025 02:40:55 -0500 Received: from mgamail.intel.com ([198.175.65.14]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tpjN6-00062i-V3 for qemu-devel@nongnu.org; Wed, 05 Mar 2025 02:40:55 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1741160453; x=1772696453; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=tQn0UJdEVPQPAmtED9qfjKDrEArx0CGf8L8FI8pp5fQ=; b=XO2t0Kk/MLdUmXNOC5iqoZIMOX3PeNv5yAXvcktPK1DnbYAHF/BCZotI prP7Q77Uvyu2m4gAUk06bc/JmJvfsvsoDkEGVn/tCBjYdIxBF9StLkFjC C2gnsYN+tc+1V3yNCXlfFDgQSbn4b8XSC43jV6/j5EWFwmkXX1UPSypCZ ZzWE+98ll03iD1LMRnY5IiLrKbOH3zk2xm7p0jlQmhYuKxtgWgK1yF4jv J1PfAC+Cv8A7fkc/EAILf0u5GGBnQclcZ+BzFS+LBZaiQJVeJFn+0HieE lT62azNx0ySKgKMYDSHssDXhK4/kjWkKaGwosAYIpKX1b2wABhTd9Yvzw Q==; X-CSE-ConnectionGUID: /f7yxjt5TM21eC3I+yImfA== X-CSE-MsgGUID: 0RpyQI3bQtCfu4LSLTl8OA== X-IronPort-AV: E=McAfee;i="6700,10204,11363"; a="45882609" X-IronPort-AV: E=Sophos;i="6.14,222,1736841600"; d="scan'208";a="45882609" Received: from fmviesa003.fm.intel.com ([10.60.135.143]) by orvoesa106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Mar 2025 23:35:11 -0800 X-CSE-ConnectionGUID: IiraRj1GR8q/NJTCULxwwA== X-CSE-MsgGUID: SXYI5W78S2yQVy+/8PczZg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,224,1728975600"; d="scan'208";a="122753370" Received: from unknown (HELO [10.238.2.135]) ([10.238.2.135]) by fmviesa003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Mar 2025 23:35:06 -0800 Message-ID: <5f76ce8f-5f69-4a95-8c27-011a7d713fc3@linux.intel.com> Date: Wed, 5 Mar 2025 15:35:04 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 10/10] 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, zhenyuw@linux.intel.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 References: <20250302220112.17653-1-dongli.zhang@oracle.com> <20250302220112.17653-11-dongli.zhang@oracle.com> Content-Language: en-US From: "Mi, Dapeng" In-Reply-To: <20250302220112.17653-11-dongli.zhang@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Received-SPF: none client-ip=198.175.65.14; 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 3/3/2025 6:00 AM, Dongli Zhang wrote: > 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. > > In additional, PMU MSRs are set only at levels >= KVM_PUT_RESET_STATE, > excluding runtime. Therefore, updating these MSRs without stopping events > should be acceptable. Suppose this works for upcoming mediated vPMU as well? If so, please mention it here. Thanks. > > Finally, 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. > > 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 > --- > 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 c5911baef0..4902694129 100644 > --- a/target/i386/kvm/kvm.c > +++ b/target/i386/kvm/kvm.c > @@ -4160,13 +4160,6 @@ static int kvm_put_msrs(X86CPU *cpu, int level) > } > > if (IS_INTEL_CPU(env) && has_pmu_version > 0) { > - if (has_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]); > @@ -4182,8 +4175,6 @@ 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,