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 B1D00CCFA13 for ; Mon, 10 Nov 2025 16:02:41 +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:MIME-Version:References:In-Reply-To:Message-ID:Subject:CC:To: From:Date:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=oaEmd1C0qTUrROe6aqZ7ZbmHO/TmwlIL1i9F68uPH/4=; b=whh9fy9yYR3LEW8er/z/MwWioB iMVSNV+2FPsU/iLxu7xh5i/wI2wPrAkEOFCD96AFurBf99nfhywmC1OJJJkKM7Q4FSQTlOraHwKv/ E9LxLGLO0/EKdxRPN1b31MOzZAJDT4ncOnTSjaAFm1mwX9uu61ylbuf0vRUlW2Ga4P1FM006zyMyE c+Ov8YVNKp2zczwCU3K7Zplpi0Knrgzd6Z5TwzPk3txc0rgL3wTpKInNusp/V4LUJ63FthDwFg7JA 34crPoqDuAh5JsJ/64YloarZtVWmxpdh2DY9xQGuJzuXCh7DixzeLL2KiufWtwSlByDopbshGcL7t bhrCF7XA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vIULg-00000005l1s-2ZHY; Mon, 10 Nov 2025 16:02:32 +0000 Received: from frasgout.his.huawei.com ([185.176.79.56]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vIULd-00000005l18-0mID for linux-arm-kernel@lists.infradead.org; Mon, 10 Nov 2025 16:02:31 +0000 Received: from mail.maildlp.com (unknown [172.18.186.216]) by frasgout.his.huawei.com (SkyGuard) with ESMTPS id 4d4vYW71dQzJ46YC; Tue, 11 Nov 2025 00:01:51 +0800 (CST) Received: from dubpeml100005.china.huawei.com (unknown [7.214.146.113]) by mail.maildlp.com (Postfix) with ESMTPS id 704A31402FF; Tue, 11 Nov 2025 00:02:21 +0800 (CST) Received: from localhost (10.203.177.15) by dubpeml100005.china.huawei.com (7.214.146.113) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.36; Mon, 10 Nov 2025 16:02:20 +0000 Date: Mon, 10 Nov 2025 16:02:18 +0000 From: Jonathan Cameron To: Ben Horgan CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH 04/33] ACPI / PPTT: Find cache level by cache-id Message-ID: <20251110160218.00001d65@huawei.com> In-Reply-To: <20251107123450.664001-5-ben.horgan@arm.com> References: <20251107123450.664001-1-ben.horgan@arm.com> <20251107123450.664001-5-ben.horgan@arm.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.42; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.203.177.15] X-ClientProxiedBy: lhrpeml100010.china.huawei.com (7.191.174.197) To dubpeml100005.china.huawei.com (7.214.146.113) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251110_080229_513120_3C749A8E X-CRM114-Status: GOOD ( 28.63 ) 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 Fri, 7 Nov 2025 12:34:21 +0000 Ben Horgan wrote: > From: James Morse > > The MPAM table identifies caches by id. The MPAM driver also wants to know > the cache level to determine if the platform is of the shape that can be > managed via resctrl. Cacheinfo has this information, but only for CPUs that > are online. > > Waiting for all CPUs to come online is a problem for platforms where > CPUs are brought online late by user-space. > > Add a helper that walks every possible cache, until it finds the one > identified by cache-id, then return the level. > > Signed-off-by: James Morse > Signed-off-by: Ben Horgan A few things inline. > --- > Changes since v3: > Tags dropped due to rework > Fallout/simplification from adding acpi_pptt_cache_v1_full > Look for each cache type before incrementing level > --- > drivers/acpi/pptt.c | 63 ++++++++++++++++++++++++++++++++++++++++++++ > include/linux/acpi.h | 5 ++++ > 2 files changed, 68 insertions(+) > > diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c > index 1ed2099c0d1a..71841c106020 100644 > --- a/drivers/acpi/pptt.c > +++ b/drivers/acpi/pptt.c > @@ -918,3 +918,66 @@ void acpi_pptt_get_cpus_from_container(u32 acpi_cpu_id, cpumask_t *cpus) > entry->length); > } > } > + > +/** > + * find_acpi_cache_level_from_id() - Get the level of the specified cache > + * @cache_id: The id field of the cache > + * > + * Determine the level relative to any CPU for the cache identified by > + * cache_id. This allows the property to be found even if the CPUs are offline. > + * > + * The returned level can be used to group caches that are peers. > + * > + * The PPTT table must be rev 3 or later. > + * > + * If one CPU's L2 is shared with another CPU as L3, this function will return > + * an unpredictable value. > + * > + * Return: -ENOENT if the PPTT doesn't exist, the revision isn't supported or > + * the cache cannot be found. > + * Otherwise returns a value which represents the level of the specified cache. > + */ > +int find_acpi_cache_level_from_id(u32 cache_id) > +{ > + int cpu; > + struct acpi_table_header *table; > + > + table = acpi_get_pptt(); > + if (!table) > + return -ENOENT; > + > + if (table->revision < 3) > + return -ENOENT; > + > + for_each_possible_cpu(cpu) { > + bool not_empty = true; > + u32 acpi_cpu_id; > + struct acpi_pptt_cache_v1_full *cache; > + struct acpi_pptt_processor *cpu_node; > + > + acpi_cpu_id = get_acpi_id_for_cpu(cpu); Might as well combine this one with declaration. > + cpu_node = acpi_find_processor_node(table, acpi_cpu_id); > + if (!cpu_node) > + continue; > + > + for (int level = 1; not_empty; level++) { This smells very much like a while loop rather than a for loop. Make it a do/while and you can avoid the somewhat nasty setting not_empty = true just to get in for first iteration. int level = 1; do { int cache_type[] = { CACHE_TYPE_INST, CACHE_TYPE_DATA, CACHE_TYPE_UNIFIED }; not_empty = false; for (int i = 0; i < ARRAY_SIZE(cache_type); i++) { cache = acpi_find_cache_node(table, acpi_cpu_id, cache_type[i], level, &cpu_node); if (!cache) continue; not_empty = true; if (acpi_pptt_cache_id_is_valid(cache) && cache->extra.cache_id == cache_id) return level; } } while (not_empty); Maybe flip sense of that bool to be empty and !empty for the test. > + int cache_type[] = {CACHE_TYPE_INST, CACHE_TYPE_DATA, CACHE_TYPE_UNIFIED}; > + > + not_empty = false; > + for (int i = 0; i < ARRAY_SIZE(cache_type); i++) { > + cache = acpi_find_cache_node(table, acpi_cpu_id, cache_type[i], > + level, &cpu_node); > + if (!cache) > + continue; > + > + not_empty = true; > + > + if (acpi_pptt_cache_id_is_valid(cache) && > + cache->extra.cache_id == cache_id) > + return level; > + } > + } > + } > + > + return -ENOENT; > +}