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 6D692C282D2 for ; Mon, 3 Mar 2025 14:46:14 +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-Transfer-Encoding: Content-Type:In-Reply-To:MIME-Version:Date:Message-ID:From:References:To: Subject:CC:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=3EZS2ejN/6IHQgzRU3+5eiINWlW/7ry7xdj6V0o4hnM=; b=gVunHgwAGrV2s2WRrorfGo/Lpf 5Ey84THHWsAT4aD2aobj8Iu771ybMGZHpmUlu0giBjhmmqrL+wSrRj+GlKLqs/5lK/23WjDQvEs8c mwolsFp34EcQbFCzW7KYhbYDQW1QTSfVSpRZuJOhH+n+VS9h0cqoo8uftbAljxSNvx57Z/r2aeYvS kbxtSiljF5wn2opWW/PI1vzS82yyTOVOJmWkiNAYBPq/XVaHU5jZ0IDEoQL39XDGjSTq6A0RvWq9p zb6ubV4atSlAT4SGHAm0im8AeTwsyoCZ626D1FXr9YBpYVLBHR0RKGxTu6lHoSDrM8hTFnWR3ACvs p7w+8DOw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tp73T-00000001A1H-3P1u; Mon, 03 Mar 2025 14:46:03 +0000 Received: from szxga02-in.huawei.com ([45.249.212.188]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tp70D-000000019NS-3IGI for linux-arm-kernel@lists.infradead.org; Mon, 03 Mar 2025 14:42:45 +0000 Received: from mail.maildlp.com (unknown [172.19.88.194]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Z61fM48jHzCs7q; Mon, 3 Mar 2025 22:39:07 +0800 (CST) Received: from kwepemd200014.china.huawei.com (unknown [7.221.188.8]) by mail.maildlp.com (Postfix) with ESMTPS id 7A0071401F0; Mon, 3 Mar 2025 22:42:36 +0800 (CST) Received: from [10.67.121.177] (10.67.121.177) 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; Mon, 3 Mar 2025 22:42:35 +0800 CC: , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v11 3/4] arm64: topology: Support SMT control on ACPI based system To: Hanjun Guo References: <20250218141018.18082-1-yangyicong@huawei.com> <20250218141018.18082-4-yangyicong@huawei.com> <92193a09-271e-895e-f77f-d3952bdfdf49@huawei.com> From: Yicong Yang Message-ID: <5f56d0fc-7ca8-cc52-9747-aec981e42bdc@huawei.com> Date: Mon, 3 Mar 2025 22:42:34 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 MIME-Version: 1.0 In-Reply-To: <92193a09-271e-895e-f77f-d3952bdfdf49@huawei.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.121.177] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) 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-20250303_064242_275326_26DF9822 X-CRM114-Status: GOOD ( 25.92 ) 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 On 2025/2/25 14:08, Hanjun Guo wrote: > On 2025/2/18 22:10, Yicong Yang wrote: >> 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 > > Looks good to me, > > Reviewed-by: Hanjun Guo > Thanks a lot for taking a look :)