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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 BE51DC282C6 for ; Mon, 3 Mar 2025 11:17:07 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4Z5x9G2wpSz2y34; Mon, 3 Mar 2025 22:17:06 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1741000626; cv=none; b=MBUXqOlMJ9unwiVQs+9eNvF2g8MuEGGEVjNbBYb7WhWeBUow2IwtQSLb2t84hq414ufL1mki1bIuRePIV95Q5/0ha3YkiUPBGx+QxLX2BmBSbaOvl9JjIa+6ZLOzBwbE5krJH6KNS9288p738GIeXSsRmmxnZYjHRYsp5Ma53bkzrxQMuBEnM/HGO6CbmGT1XZweVgjIDiGyRnaVgCv9nd3etOQKkfCjgAzM2Jas4shUqc6Dvy504ZvJx6zeu/wcE+mbf3PUWqdLijDqmpOsat0xx4EWiWV4N4boy5mKXrlB3tbAGOFYWaxlfEsWEitBvyLfjFETpNHH33jM7EZL9w== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1741000626; c=relaxed/relaxed; bh=ym2vB8taCXVhXuUVrfzAT1jmbvDb6jkdVJy/SrgbKTc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OC6msiLBgPo5gVRphPtOz/Pc83bTse9imQUMRvRL1prlfHLwM0ph+SjE+sFd0VdAc/KzYja/eakCJY8/TmScosT88z9/8JezI4M4OZXaYKnu+wbmnSxODw4aMu79wN9omvGUlBCc8JEgqXZ3R0H3fG/M0dury8x/rXvumkydIHGhtvitJlK8UtoxTXYoH/+QVfgGOWzQK1O0BOEYk7Y3f05+9otAAalnXAXK1LN8JKf3N6WKisbWoMlS6DGYCoGa4NGNU9DdonuGK7fDkWMpglrWX0qu4mIpHidNClRXCYR2fcU/KXMPxgn9k/vk+iPuefY2JRO2nqb0MlwGNuP/bg== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass (client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=sudeep.holla@arm.com; receiver=lists.ozlabs.org) smtp.mailfrom=arm.com Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=arm.com (client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=sudeep.holla@arm.com; receiver=lists.ozlabs.org) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lists.ozlabs.org (Postfix) with ESMTP id 4Z5x9F1Vlvz2xdg for ; Mon, 3 Mar 2025 22:17:03 +1100 (AEDT) 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 5FC8E113E; Mon, 3 Mar 2025 03:16:45 -0800 (PST) Received: from bogus (e133711.arm.com [10.1.196.55]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0CDCF3F673; Mon, 3 Mar 2025 03:16:26 -0800 (PST) Date: Mon, 3 Mar 2025 11:16:24 +0000 From: Sudeep Holla To: Pierre Gondois Cc: Yicong Yang , , Sudeep Holla , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v11 3/4] arm64: topology: Support SMT control on ACPI based system Message-ID: References: <20250218141018.18082-1-yangyicong@huawei.com> <20250218141018.18082-4-yangyicong@huawei.com> <336e9c4e-cd9c-4449-ba7b-60ee8774115d@arm.com> <20250228190641.q23vd53aaw42tcdi@bogus> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Mar 03, 2025 at 10:56:12AM +0100, Pierre Gondois wrote: > On 2/28/25 20:06, Sudeep Holla wrote: > > > > > > > > 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. > > > > > > > Sure, what I meant is to have max_smt_thread_num set to 1 by default is > > that is what needed anyways and the above code does that now. > > > > Why not start with initialised to 1 instead ? > > Of course some current logic needs to change around testing it for zero. > > > > I think there would still be a way to check against the default value. > If we have: > unsigned int max_smt_thread_num = 1; > > then on a platform with 2 threads, the detection condition would trigger: > xa_for_each(&hetero_cpu, hetero_id, entry) { > if (entry->thread_num != max_smt_thread_num && max_smt_thread_num) <---- (entry->thread_num=2) and (max_smt_thread_num=1) > pr_warn_once("Heterogeneous SMT topology is partly > supported by SMT control\n"); > > so we would need an additional variable: > bool is_initialized = false; Sure, we could do that or skip the check if max_smt_thread_num == 1 ? I mean if (entry->thread_num != max_smt_thread_num && max_smt_thread_num != 1) I assume entry->thread_num must be set to 1 on single threaded cores Won't that work ? Am I missing something still ? -- Regards, Sudeep