From patchwork Mon Jan 8 08:27:17 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhao Liu X-Patchwork-Id: 13513108 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.9]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E629010A2C for ; Mon, 8 Jan 2024 08:14:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="Q8a6fdbH" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1704701698; x=1736237698; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=xMM9uHYzZgcNWhqwDNJq2lnGBNKGHDs1fTg/xiT5xz4=; b=Q8a6fdbHEVHtPkRTZFzESwwUwrwOS6Q9N/mC1aaecL0JKoEmU/PDzTZo I1K/5EWZONgWglsJYtUluKEsA+2SkdhuQotBIwqxwAaaise+eTRTXZ9Pz DYIgV8VTp7c/SlcGu+/Uwa7HyyPcc2qFVArty26rWWpJbPrm38wFbadHs 0gd3+eOsJnEmp9LpWDOHksqVn+7RdKBp1lWTSZf8tVwSE0JVXAO9khRhU xCkHJFgEV0tYb36DN7Y1Hp+gleZqfJtwtCcFhWmbwIj31uvWIKUPIDsu+ cuwvKvYPutRPtw7kyugza43ScCY779whWShiwJEvJpUW02igxFIB8eeSQ A==; X-IronPort-AV: E=McAfee;i="6600,9927,10946"; a="16419968" X-IronPort-AV: E=Sophos;i="6.04,340,1695711600"; d="scan'208";a="16419968" Received: from fmviesa002.fm.intel.com ([10.60.135.142]) by orvoesa101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Jan 2024 00:14:58 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.04,340,1695711600"; d="scan'208";a="15850187" Received: from liuzhao-optiplex-7080.sh.intel.com ([10.239.160.36]) by fmviesa002.fm.intel.com with ESMTP; 08 Jan 2024 00:14:54 -0800 From: Zhao Liu To: Eduardo Habkost , Marcel Apfelbaum , "Michael S . Tsirkin" , Richard Henderson , Paolo Bonzini , Marcelo Tosatti Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, Zhenyu Wang , Zhuocheng Ding , Zhao Liu , Babu Moger , Yongwei Ma Subject: [PATCH v7 06/16] i386: Introduce module-level cpu topology to CPUX86State Date: Mon, 8 Jan 2024 16:27:17 +0800 Message-Id: <20240108082727.420817-7-zhao1.liu@linux.intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240108082727.420817-1-zhao1.liu@linux.intel.com> References: <20240108082727.420817-1-zhao1.liu@linux.intel.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Zhuocheng Ding smp command has the "clusters" parameter but x86 hasn't supported that level. "cluster" is a CPU topology level concept above cores, in which the cores may share some resources (L2 cache or some others like L3 cache tags, depending on the Archs) [1][2]. For x86, the resource shared by cores at the cluster level is mainly the L2 cache. However, using cluster to define x86's L2 cache topology will cause the compatibility problem: Currently, x86 defaults that the L2 cache is shared in one core, which actually implies a default setting "cores per L2 cache is 1" and therefore implicitly defaults to having as many L2 caches as cores. For example (i386 PC machine): -smp 16,sockets=2,dies=2,cores=2,threads=2,maxcpus=16 (*) Considering the topology of the L2 cache, this (*) implicitly means "1 core per L2 cache" and "2 L2 caches per die". If we use cluster to configure L2 cache topology with the new default setting "clusters per L2 cache is 1", the above semantics will change to "2 cores per cluster" and "1 cluster per L2 cache", that is, "2 cores per L2 cache". So the same command (*) will cause changes in the L2 cache topology, further affecting the performance of the virtual machine. Therefore, x86 should only treat cluster as a cpu topology level and avoid using it to change L2 cache by default for compatibility. "cluster" in smp is the CPU topology level which is between "core" and die. For x86, the "cluster" in smp is corresponding to the module level [2], which is above the core level. So use the "module" other than "cluster" in i386 code. And please note that x86 already has a cpu topology level also named "cluster" [3], this level is at the upper level of the package. Here, the cluster in x86 cpu topology is completely different from the "clusters" as the smp parameter. After the module level is introduced, the cluster as the smp parameter will actually refer to the module level of x86. [1]: 864c3b5c32f0 ("hw/core/machine: Introduce CPU cluster topology support") [2]: Yanan's comment about "cluster", https://lists.gnu.org/archive/html/qemu-devel/2023-02/msg04051.html [3]: SDM, vol.3, ch.9, 9.9.1 Hierarchical Mapping of Shared Resources. Signed-off-by: Zhuocheng Ding Co-developed-by: Zhao Liu Signed-off-by: Zhao Liu Tested-by: Babu Moger Tested-by: Yongwei Ma Acked-by: Michael S. Tsirkin --- Changes since v1: * The background of the introduction of the "cluster" parameter and its exact meaning were revised according to Yanan's explanation. (Yanan) --- hw/i386/x86.c | 1 + target/i386/cpu.c | 1 + target/i386/cpu.h | 5 +++++ 3 files changed, 7 insertions(+) diff --git a/hw/i386/x86.c b/hw/i386/x86.c index 2b6291ad8d5f..1d19a8c609b1 100644 --- a/hw/i386/x86.c +++ b/hw/i386/x86.c @@ -310,6 +310,7 @@ void x86_cpu_pre_plug(HotplugHandler *hotplug_dev, init_topo_info(&topo_info, x86ms); env->nr_dies = ms->smp.dies; + env->nr_modules = ms->smp.clusters; /* * If APIC ID is not set, diff --git a/target/i386/cpu.c b/target/i386/cpu.c index 5c295c9a9e2d..0a2ce9b92b1f 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -7699,6 +7699,7 @@ static void x86_cpu_initfn(Object *obj) CPUX86State *env = &cpu->env; env->nr_dies = 1; + env->nr_modules = 1; object_property_add(obj, "feature-words", "X86CPUFeatureWordInfo", x86_cpu_get_feature_words, diff --git a/target/i386/cpu.h b/target/i386/cpu.h index 9c78cfc3f322..eecd30bde92b 100644 --- a/target/i386/cpu.h +++ b/target/i386/cpu.h @@ -1904,6 +1904,11 @@ typedef struct CPUArchState { /* Number of dies within this CPU package. */ unsigned nr_dies; + /* + * Number of modules within this CPU package. + * Module level in x86 cpu topology is corresponding to smp.clusters. + */ + unsigned nr_modules; } CPUX86State; struct kvm_msrs;