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 783E8D5E147 for ; Fri, 8 Nov 2024 08:09:00 +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=syaFfjwerqR8utu0oNjnVZRq4peXobeHGKBHeZI/wa8=; b=XW9+TdQDNc4yiUsBVeBSIre6ef YS3gKj4xGpOOt/dSNTeaZ4k4llGp+mNQTZv0AeZly53Epf6cs1QqG9wTs3dfZ4QPc5uAdeqI5n9I1 shDNkVlNSgYrm448z1vGr8GQdL49Xuq2i3/uizXcvzekje1NFFRW4h1h3XxplfAG+6jp4ZHqjYxMV g5YXwbkKApC/D/7EBd5GsQSvUBzWRhcweEDqUuSFrJHY065jGTFd3i8CRV6ri2ylU7lTiA8Mg3Cq3 IZM4Css5XDDuToHdmsbVsqLt2vy0En7u404AG4ntXauEGhNLY8QpOWV7V0UljJfIcY080kv74fZGI /wXZvBsg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t9K2x-00000009ilv-27bw; Fri, 08 Nov 2024 08:08:47 +0000 Received: from szxga08-in.huawei.com ([45.249.212.255]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1t9K1A-00000009iRa-1KSu for linux-arm-kernel@lists.infradead.org; Fri, 08 Nov 2024 08:06:58 +0000 Received: from mail.maildlp.com (unknown [172.19.163.252]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4XlBL52N1bz1T9sv; Fri, 8 Nov 2024 16:04:29 +0800 (CST) Received: from kwepemd200014.china.huawei.com (unknown [7.221.188.8]) by mail.maildlp.com (Postfix) with ESMTPS id BB09B1800D9; Fri, 8 Nov 2024 16:06:51 +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; Fri, 8 Nov 2024 16:06:50 +0800 CC: , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v7 3/4] arm64: topology: Support SMT control on ACPI based system To: Pierre Gondois References: <20241030125415.18994-1-yangyicong@huawei.com> <20241030125415.18994-4-yangyicong@huawei.com> <63792865-46ad-44a5-a1f2-9a17da5b4bfc@arm.com> From: Yicong Yang Message-ID: <93a8b799-dfd9-5ffa-37ca-e7cd4a82e70e@huawei.com> Date: Fri, 8 Nov 2024 16:06:50 +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: <63792865-46ad-44a5-a1f2-9a17da5b4bfc@arm.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.121.177] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) 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-20241108_000656_725928_F9CE4958 X-CRM114-Status: GOOD ( 20.59 ) 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 2024/11/8 1:20, Pierre Gondois wrote: > > > On 10/30/24 13:54, 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 >> Signed-off-by: Yicong Yang >> --- >>   arch/arm64/kernel/topology.c | 57 ++++++++++++++++++++++++++++++++++++ >>   1 file changed, 57 insertions(+) >> [...] >> @@ -67,6 +106,24 @@ 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"); >> + >> +        if (entry->thread_num > max_smt_thread_num) >> +            max_smt_thread_num = entry->thread_num; >> + >> +        xa_erase(&hetero_cpu, hetero_id); >> +        kfree(entry); >> +    } > > I think you need to check that max_smt_thread_num !=0, > like in the DT path. Otherwise on a platform with no SMT, > max_smt_thread_num = 0 and I hit: > > kernel/cpu::cpu_smt_set_num_threads() > WARN_ON(!num_threads || (num_threads > max_threads)); > > > -> > if (max_smt_thread_num) >     cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num); > sorry for this silly mistake. yes we should do the same like in the DT path. I'll get this fixed. thanks for testing. >> + >> +    cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num); >> +    xa_destroy(&hetero_cpu); >>       return 0; >>   } >>   #endif > > .