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 EF55CC83F26 for ; Mon, 28 Jul 2025 09:03:42 +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=1R3wLojHI2jyxLalrUt6NRLinefciF1M/4eq+YtOci0=; b=r4oByV87Uq+aZK12QCaNJfeY7t BGaYZhaeZFjP8xTVytcNX/y+zDN0iW9PO/ekXEw6iBTJNeM9RTO8OXbZX+ZyateOKSgh9Iji/dpbo Fwya1TqwEoCiDVCliSG2GGp60ypz65En5ckflwAADj8l81hEH7cfSlb/n3gwYi/dywwt2Ajj/kupL M0Eki8KAemDB0RjrXE4WRkkU/Gnu+rjs7QlFYt9hEQ8/uRXi85Tt7qfCVLAXcfImrug8dX7tFBoFr 7nzXg/uZZXX4upIBuQGp9/JGJi+JzJQi8B+JTm1qZmwTfFvmVUBzLGvSsW7RqsQh0BJi7m/lMB/iO sPO1dilg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1ugJlh-0000000E3Bm-41Xp; Mon, 28 Jul 2025 09:03:37 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1ugJMn-0000000E0lE-0h8g for linux-arm-kernel@lists.infradead.org; Mon, 28 Jul 2025 08:37:54 +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 1ECAC1596; Mon, 28 Jul 2025 01:37:42 -0700 (PDT) Received: from [10.1.196.46] (e134344.arm.com [10.1.196.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 26F6A3F673; Mon, 28 Jul 2025 01:37:46 -0700 (PDT) Message-ID: Date: Mon, 28 Jul 2025 09:37:44 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 04/36] cacheinfo: Expose the code to generate a cache-id from a device_node To: James Morse , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Rob Herring , Rohit Mathew , Shanker Donthineni , Zeng Heng , Lecopzer Chen , Carl Worth , shameerali.kolothum.thodi@huawei.com, D Scott Phillips OS , lcherian@marvell.com, bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com, dfustini@baylibre.com, amitsinght@marvell.com, David Hildenbrand , Rex Nie , Dave Martin , Koba Ko References: <20250711183648.30766-1-james.morse@arm.com> <20250711183648.30766-5-james.morse@arm.com> Content-Language: en-US From: Ben Horgan In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250728_013753_301235_24F819E9 X-CRM114-Status: GOOD ( 16.45 ) 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 Hi James, On 7/25/25 18:08, James Morse wrote: > Hi Ben, > > On 14/07/2025 12:40, Ben Horgan wrote: >> On 7/11/25 19:36, James Morse wrote: >>> The MPAM driver identifies caches by id for use with resctrl. It >>> needs to know the cache-id when probe-ing, but the value isn't set >>> in cacheinfo until device_initcall(). >>> >>> Expose the code that generates the cache-id. The parts of the MPAM >>> driver that run early can use this to set up the resctrl structures >>> before cacheinfo is ready in device_initcall(). > >>> diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c >>> index 613410705a47..0fdd6358ee73 100644 >>> --- a/drivers/base/cacheinfo.c >>> +++ b/drivers/base/cacheinfo.c >>> @@ -207,8 +207,7 @@ static bool match_cache_node(struct device_node *cpu, >>>   #define arch_compact_of_hwid(_x)    (_x) >>>   #endif >>>   -static void cache_of_set_id(struct cacheinfo *this_leaf, >>> -                struct device_node *cache_node) >>> +unsigned long cache_of_calculate_id(struct device_node *cache_node) >>>   { >>>       struct device_node *cpu; >>>       u32 min_id = ~0; >>> @@ -219,15 +218,23 @@ static void cache_of_set_id(struct cacheinfo *this_leaf, >>>           id = arch_compact_of_hwid(id); >>>           if (FIELD_GET(GENMASK_ULL(63, 32), id)) { >>>               of_node_put(cpu); >>> -            return; >>> +            return ~0UL; >>>           } >>>             if (match_cache_node(cpu, cache_node)) >>>               min_id = min(min_id, id); >>>       } >>>   -    if (min_id != ~0) { >>> -        this_leaf->id = min_id; >>> +    return min_id; > >> Looks like some 32bit/64bit confusion. Don't we want to return ~0UL if min_id == ~0? > > Certainly some confusion - yup, because cache_of_calculate_id() needs to return something > that is out of range and (u32)-1 might be valid... > > I think changing min_id to be defined as: > | unsigned long min_id = ~0UL; > > fixes this - any trip round the loop that doesn't match anything will eventually return ~0UL. Yes, that would work. > > > Thanks! - I always get the 'UL' suffixes wrong. > > James Thanks, Ben