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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 00903C02198 for ; Tue, 18 Feb 2025 14:14:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type: Content-Transfer-Encoding:MIME-Version:References:In-Reply-To:Message-ID:Date :Subject:CC:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ofjcbTC5Iths2yPSWOVtIfXGjT3o/MqZin0E+e7oyZc=; b=TG5OgPMkUEtrs1iNFZTFlsGvJY Hq95r+xFiKtHIT6HnTg/cXSvagi2QI3hipsGOrFnaje/IfblxhBgqOx52olpTdUYhMJMHsHHFfcEG d7hjJhIUwTMQ9lvrygATarmDrih9cLHdzSBgCXOVPjMIH+NDJOljX89/QtMEJu6KrDu+NYFbYZeNJ moC6CG6TsUtNHuoKhzTrKAlb02BP+0iodDt079gVmv8H7Rri9F+OAbgWj500TyblvmaT0Kh1u/KYM 5TAQO7ps6+0g/NBd7KsZ1Nl4CjZrtmV/891oxQUKIpBq9rJrATF6aIWIjHGwlQrMWnYvmS0Fvp08T wURcqCUg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tkON4-00000008Sj7-42G3; Tue, 18 Feb 2025 14:14:46 +0000 Received: from szxga04-in.huawei.com ([45.249.212.190]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tkOIk-00000008RiS-1PNp for linux-arm-kernel@lists.infradead.org; Tue, 18 Feb 2025 14:10:20 +0000 Received: from mail.maildlp.com (unknown [172.19.163.44]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4Yy1YV4MQsz22wPM; Tue, 18 Feb 2025 22:07:10 +0800 (CST) Received: from kwepemd200014.china.huawei.com (unknown [7.221.188.8]) by mail.maildlp.com (Postfix) with ESMTPS id 0F5211401F1; Tue, 18 Feb 2025 22:10:10 +0800 (CST) Received: from localhost.localdomain (10.50.165.33) by kwepemd200014.china.huawei.com (7.221.188.8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1258.34; Tue, 18 Feb 2025 22:10:08 +0800 From: Yicong Yang To: , , , , , , , , , , , CC: , , , , , , , , , , , , , Subject: [PATCH v11 3/4] arm64: topology: Support SMT control on ACPI based system Date: Tue, 18 Feb 2025 22:10:17 +0800 Message-ID: <20250218141018.18082-4-yangyicong@huawei.com> X-Mailer: git-send-email 2.31.0 In-Reply-To: <20250218141018.18082-1-yangyicong@huawei.com> References: <20250218141018.18082-1-yangyicong@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.50.165.33] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemd200014.china.huawei.com (7.221.188.8) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250218_061018_840908_89872C24 X-CRM114-Status: GOOD ( 23.03 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Yicong Yang For ACPI we'll build the topology from PPTT and we cannot directly get the SMT number of each core. Instead using a temporary xarray to record the heterogeneous information (from ACPI_PPTT_ACPI_IDENTICAL) and SMT information of the first core in its heterogeneous CPU cluster when building the topology. Then we can know the largest SMT number in the system. If a homogeneous system's using ACPI 6.2 or later, all the CPUs should be under the root node of PPTT. There'll be only one entry in the xarray and all the CPUs in the system will be assumed identical. The core's SMT control provides two interface to the users [1]: 1) enable/disable SMT by writing on/off 2) enable/disable SMT by writing thread number 1/max_thread_number If a system have more than one SMT thread number the 2) may not handle it well, since there're multiple thread numbers in the system and 2) only accept 1/max_thread_number. So issue a warning to notify the users if such system detected. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/ABI/testing/sysfs-devices-system-cpu#n542 Reviewed-by: Jonathan Cameron Signed-off-by: Yicong Yang --- arch/arm64/kernel/topology.c | 66 ++++++++++++++++++++++++++++++++++++ 1 file changed, 66 insertions(+) diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c index 1a2c72f3e7f8..6eba1ac091ee 100644 --- a/arch/arm64/kernel/topology.c +++ b/arch/arm64/kernel/topology.c @@ -15,8 +15,10 @@ #include #include #include +#include #include #include +#include #include #include @@ -37,17 +39,28 @@ static bool __init acpi_cpu_is_threaded(int cpu) return !!is_threaded; } +struct cpu_smt_info { + unsigned int thread_num; + int core_id; +}; + /* * Propagate the topology information of the processor_topology_node tree to the * cpu_topology array. */ int __init parse_acpi_topology(void) { + unsigned int max_smt_thread_num = 0; + struct cpu_smt_info *entry; + struct xarray hetero_cpu; + unsigned long hetero_id; int cpu, topology_id; if (acpi_disabled) return 0; + xa_init(&hetero_cpu); + for_each_possible_cpu(cpu) { topology_id = find_acpi_cpu_topology(cpu, 0); if (topology_id < 0) @@ -57,6 +70,34 @@ int __init parse_acpi_topology(void) cpu_topology[cpu].thread_id = topology_id; topology_id = find_acpi_cpu_topology(cpu, 1); cpu_topology[cpu].core_id = topology_id; + + /* + * In the PPTT, CPUs below a node with the 'identical + * implementation' flag have the same number of threads. + * Count the number of threads for only one CPU (i.e. + * one core_id) among those with the same hetero_id. + * See the comment of find_acpi_cpu_topology_hetero_id() + * for more details. + * + * One entry is created for each node having: + * - the 'identical implementation' flag + * - its parent not having the flag + */ + hetero_id = find_acpi_cpu_topology_hetero_id(cpu); + entry = xa_load(&hetero_cpu, hetero_id); + if (!entry) { + entry = kzalloc(sizeof(*entry), GFP_KERNEL); + WARN_ON_ONCE(!entry); + + if (entry) { + entry->core_id = topology_id; + entry->thread_num = 1; + xa_store(&hetero_cpu, hetero_id, + entry, GFP_KERNEL); + } + } else if (entry->core_id == topology_id) { + entry->thread_num++; + } } else { cpu_topology[cpu].thread_id = -1; cpu_topology[cpu].core_id = topology_id; @@ -67,6 +108,31 @@ int __init parse_acpi_topology(void) cpu_topology[cpu].package_id = topology_id; } + /* + * This should be a short loop depending on the number of heterogeneous + * CPU clusters. Typically on a homogeneous system there's only one + * entry in the XArray. + */ + xa_for_each(&hetero_cpu, hetero_id, entry) { + if (entry->thread_num != max_smt_thread_num && max_smt_thread_num) + pr_warn_once("Heterogeneous SMT topology is partly supported by SMT control\n"); + + max_smt_thread_num = max(max_smt_thread_num, entry->thread_num); + xa_erase(&hetero_cpu, hetero_id); + kfree(entry); + } + + /* + * Notify the CPU framework of the SMT support. Initialize the + * max_smt_thread_num to 1 if no SMT support detected. A thread + * number of 1 can be handled by the framework so we don't need + * to check max_smt_thread_num to see we support SMT or not. + */ + if (!max_smt_thread_num) + max_smt_thread_num = 1; + + cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num); + xa_destroy(&hetero_cpu); return 0; } #endif -- 2.24.0