From patchwork Mon Jan 8 08:27:12 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhao Liu X-Patchwork-Id: 13513103 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 E4C77B677 for ; Mon, 8 Jan 2024 08:14:40 +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="fY4Wgvk2" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1704701681; x=1736237681; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=QTeK4gl/qfFtAoQwuLr1k8h453tQUQfxQhq+4gyaID0=; b=fY4Wgvk2y5CwLsGQd/FRtojzEAA7h+8/xhb2Lfdj49qiddh0GwV8EU9F 8+1Cu/BsGNXO7RqfSx3i9zIzDahWc6lknDaTUUVwvQwVQ4DOSdv+tDBxn 5Uzix3zXelyLdYPhu9ozh73HnWLXndUulNlwIaUvz9KLdBfRKLYEwNPpj I7x8BUVvzk3kB3TgRsYq1j5FfjrHYo5FXgYtRkZi7fLiMNCij++a3JkVr e+mIA2Sz5zvR6LzxRYZGV8rlq3b7sMaiGqlzyig/oWGfa/2HE0KsU1ZF4 bKCVuwVWDHXKByRr7FQ6x2m3qzJcLQWhEL0y8lqx4kvARIjPpf4sJLgFT g==; X-IronPort-AV: E=McAfee;i="6600,9927,10946"; a="16419912" X-IronPort-AV: E=Sophos;i="6.04,340,1695711600"; d="scan'208";a="16419912" 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 00:14:41 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.04,340,1695711600"; d="scan'208";a="15850141" Received: from liuzhao-optiplex-7080.sh.intel.com ([10.239.160.36]) by fmviesa002.fm.intel.com with ESMTP; 08 Jan 2024 00:14:37 -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 , Robert Hoo , Xiaoyao Li , Babu Moger , Yongwei Ma Subject: [PATCH v7 01/16] i386/cpu: Fix i/d-cache topology to core level for Intel CPU Date: Mon, 8 Jan 2024 16:27:12 +0800 Message-Id: <20240108082727.420817-2-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: Zhao Liu For i-cache and d-cache, current QEMU hardcodes the maximum IDs for CPUs sharing cache (CPUID.04H.00H:EAX[bits 25:14] and CPUID.04H.01H:EAX[bits 25:14]) to 0, and this means i-cache and d-cache are shared in the SMT level. This is correct if there's single thread per core, but is wrong for the hyper threading case (one core contains multiple threads) since the i-cache and d-cache are shared in the core level other than SMT level. For AMD CPU, commit 8f4202fb1080 ("i386: Populate AMD Processor Cache Information for cpuid 0x8000001D") has already introduced i/d cache topology as core level by default. Therefore, in order to be compatible with both multi-threaded and single-threaded situations, we should set i-cache and d-cache be shared at the core level by default. This fix changes the default i/d cache topology from per-thread to per-core. Potentially, this change in L1 cache topology may affect the performance of the VM if the user does not specifically specify the topology or bind the vCPU. However, the way to achieve optimal performance should be to create a reasonable topology and set the appropriate vCPU affinity without relying on QEMU's default topology structure. Fixes: 7e3482f82480 ("i386: Helpers to encode cache information consistently") Suggested-by: Robert Hoo Signed-off-by: Zhao Liu Reviewed-by: Xiaoyao Li Tested-by: Babu Moger Tested-by: Yongwei Ma Acked-by: Michael S. Tsirkin --- Changes since v3: * Change the description of current i/d cache encoding status to avoid misleading to "architectural rules". (Xiaoyao) Changes since v1: * Split this fix from the patch named "i386/cpu: Fix number of addressable IDs in CPUID.04H". * Add the explanation of the impact on performance. (Xiaoyao) --- target/i386/cpu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/target/i386/cpu.c b/target/i386/cpu.c index 95d5f16cd5eb..5a3678a789cf 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -6113,12 +6113,12 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count, switch (count) { case 0: /* L1 dcache info */ encode_cache_cpuid4(env->cache_info_cpuid4.l1d_cache, - 1, cs->nr_cores, + cs->nr_threads, cs->nr_cores, eax, ebx, ecx, edx); break; case 1: /* L1 icache info */ encode_cache_cpuid4(env->cache_info_cpuid4.l1i_cache, - 1, cs->nr_cores, + cs->nr_threads, cs->nr_cores, eax, ebx, ecx, edx); break; case 2: /* L2 cache info */