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 59191C282D0 for ; Fri, 28 Feb 2025 17:53:56 +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:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=PPbqygpoyBv7L91MX3P42mRY8joCU0uEy0W1GnAU9WA=; b=mtXdXBeczmXjfl3XrPKuRcunoO q+iGEXEId+xDC0jPx2tGNKI91Mh4nqWbJU4f8mOhOQOQc/2Q40eaVEQ8LynEt6EK1f/yB+cZqfEwW yGKHueaK2vkj+XX4YQp/tBFttdkHCU8F6ZkbwYJ6nUGrN7orXslrdJ3qV49cnqfMfPd6QvHuPpNqO jGTMHAtPbqCnlYltiPjdPiQ9Tzsr1c3w1k4x0QX9Z5BwD1iLyIdfbatDqBPT6FNlJ6GYvb9P8y9fp ONVnTKBN6fhVqh94Cs/jFDtiuhdDOF9d3t7NC+uTilZBJV4g+X2e3f1vRlw2pfv9Zm3AHoMf2DTPl xxIOeabA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1to4YV-0000000C24e-3YMn; Fri, 28 Feb 2025 17:53:47 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1to4WJ-0000000C1Xj-2ayY for linux-arm-kernel@lists.infradead.org; Fri, 28 Feb 2025 17:51:33 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BB7121515; Fri, 28 Feb 2025 09:51:43 -0800 (PST) Received: from [10.57.38.197] (unknown [10.57.38.197]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1DCEC3F6A8; Fri, 28 Feb 2025 09:51:22 -0800 (PST) Message-ID: <336e9c4e-cd9c-4449-ba7b-60ee8774115d@arm.com> Date: Fri, 28 Feb 2025 18:51:16 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v11 3/4] arm64: topology: Support SMT control on ACPI based system To: Sudeep Holla , Yicong Yang Cc: catalin.marinas@arm.com, will@kernel.org, tglx@linutronix.de, peterz@infradead.org, mpe@ellerman.id.au, linux-arm-kernel@lists.infradead.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, dietmar.eggemann@arm.com, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, morten.rasmussen@arm.com, msuchanek@suse.de, gregkh@linuxfoundation.org, rafael@kernel.org, jonathan.cameron@huawei.com, prime.zeng@hisilicon.com, linuxarm@huawei.com, yangyicong@hisilicon.com, xuwei5@huawei.com, guohanjun@huawei.com, sshegde@linux.ibm.com References: <20250218141018.18082-1-yangyicong@huawei.com> <20250218141018.18082-4-yangyicong@huawei.com> Content-Language: en-US From: Pierre Gondois In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250228_095131_751671_3136C2C3 X-CRM114-Status: GOOD ( 29.84 ) 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 2/28/25 14:56, Sudeep Holla wrote: > On Tue, Feb 18, 2025 at 10:10:17PM +0800, 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"); > > Ditto as previous patch about handling no threaded cores with threaded cores > in the system. I am not sure if that is required but just raising it here. > >> + >> + 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; >> + > > Ditto as previous patch, can get rid if it is default 1. > On non-SMT platforms, not calling cpu_smt_set_num_threads() leaves cpu_smt_num_threads uninitialized to UINT_MAX: smt/active:0 smt/control:-1 If cpu_smt_set_num_threads() is called: active:0 control:notsupported So it might be slightly better to still initialize max_smt_thread_num. Otherwise I tested the patches on arm64 ACPI smt platforms and it worked well, so for all the patches (if there are no other major modifications): Reviewed-by: Pierre Gondois Regards, Pierre