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 18E3ACAC58D for ; Thu, 11 Sep 2025 11:00:09 +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=hwaHFWHeIfe9eoK2TB85BwsnQeyXhwwlYy5Sp9LAor8=; b=cndMqseWntzqO8XUAllY0UCUVA JXI/kcVMzIFXYrAZwmXzu1RbpNZiYGIMExbwzpwlOnFeNqTRgUEbrYK9LGDirTJsVKLe8dx8QENvE ydx2/HQUFLVoiyU5RwMQvrYu5IBrP6YLTs4IZUzFRrlq2v4ioVV5FKHICg2zURIMECd57OvZssUYj sGyRT+VxvV38FevLkSwgfgyGrZcEdrllCfcGQYX2VPOfO6onZ+B1TySfgpsVmB/EoZldodXYa2vBt fY1/sslO2KbeGvgsTh5NYY/a5u/RF2iRwgveyRBagZlrAAKd7EF1z6nbUk63FJ9TTWjGoKYmwxZDk 2/2XQV/g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uwf20-00000002Vcp-1VwC; Thu, 11 Sep 2025 11:00:00 +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 1uwf1w-00000002VaM-3flv for linux-arm-kernel@lists.infradead.org; Thu, 11 Sep 2025 10:59:58 +0000 Received: from mail.maildlp.com (unknown [172.18.186.216]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4cMvdd5XD1z6M4bQ; Thu, 11 Sep 2025 18:57:09 +0800 (CST) Received: from frapeml500008.china.huawei.com (unknown [7.182.85.71]) by mail.maildlp.com (Postfix) with ESMTPS id 86F681402F5; Thu, 11 Sep 2025 18:59:49 +0800 (CST) Received: from localhost (10.203.177.15) by frapeml500008.china.huawei.com (7.182.85.71) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.39; Thu, 11 Sep 2025 12:59:48 +0200 Date: Thu, 11 Sep 2025 11:59:46 +0100 From: Jonathan Cameron To: James Morse CC: , , , D Scott Phillips OS , , , , , , Jamie Iles , Xin Hao , , , , David Hildenbrand , Dave Martin , Koba Ko , Shanker Donthineni , , , Rob Herring , Rohit Mathew , "Rafael Wysocki" , Len Brown , Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Catalin Marinas , "Will Deacon" , Greg Kroah-Hartman , Danilo Krummrich Subject: Re: [PATCH v2 03/29] ACPI / PPTT: Find cache level by cache-id Message-ID: <20250911115946.00001752@huawei.com> In-Reply-To: <20250910204309.20751-4-james.morse@arm.com> References: <20250910204309.20751-1-james.morse@arm.com> <20250910204309.20751-4-james.morse@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: lhrpeml100012.china.huawei.com (7.191.174.184) To frapeml500008.china.huawei.com (7.182.85.71) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250911_035957_202532_5C5D025C X-CRM114-Status: GOOD ( 32.02 ) 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 Wed, 10 Sep 2025 20:42:43 +0000 James Morse wrote: > 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 > --- > Changes since v1: > * Droppeed the cleanup based table freeing, use acpi_get_pptt() instead. > * Removed a confusing comment. > * Clarified the kernel doc. > > Changes since RFC: > * acpi_count_levels() now returns a value. > * Converted the table-get stuff to use Jonathan's cleanup helper. > * Dropped Sudeep's Review tag due to the cleanup change. > --- > drivers/acpi/pptt.c | 62 ++++++++++++++++++++++++++++++++++++++++++++ > include/linux/acpi.h | 5 ++++ > 2 files changed, 67 insertions(+) > > diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c > index 7af7d62597df..c5f2a51d280b 100644 > --- a/drivers/acpi/pptt.c > +++ b/drivers/acpi/pptt.c > @@ -904,3 +904,65 @@ void acpi_pptt_get_cpus_from_container(u32 acpi_cpu_id, cpumask_t *cpus) > entry->length); > } > } > + > +/* /** It's an exposed interface so nice to have formal kernel-doc and automatic checks that brings. > + * find_acpi_cache_level_from_id() - Get the level of the specified cache > + * @cache_id: The id field of the unified cache > + * > + * Determine the level relative to any CPU for the unified 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 unified caches that are peers. Silly question but why do we care if this a unified cache? It's a bit odd to have a general sounding function fail for split caches. The handling would have to be more complex but if we really don't want to do it maybe rename the function to find_acpi_unifiedcache_level_from_id() and if the general version gets added later we can switch to that. > + * > + * The PPTT table must be rev 3 or later, > + * > + * If one CPUs L2 is shared with another 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) > +{ > + u32 acpi_cpu_id; > + int level, cpu, num_levels; > + struct acpi_pptt_cache *cache; > + struct acpi_table_header *table; > + struct acpi_pptt_cache_v1 *cache_v1; > + struct acpi_pptt_processor *cpu_node; > + > + table = acpi_get_pptt(); > + if (!table) > + return -ENOENT; > + > + if (table->revision < 3) > + return -ENOENT; > + > + for_each_possible_cpu(cpu) { > + acpi_cpu_id = get_acpi_id_for_cpu(cpu); > + cpu_node = acpi_find_processor_node(table, acpi_cpu_id); > + if (!cpu_node) > + return -ENOENT; > + num_levels = acpi_count_levels(table, cpu_node, NULL); > + > + /* Start at 1 for L1 */ > + for (level = 1; level <= num_levels; level++) { > + cache = acpi_find_cache_node(table, acpi_cpu_id, > + ACPI_PPTT_CACHE_TYPE_UNIFIED, > + level, &cpu_node); > + if (!cache) > + continue; > + > + cache_v1 = ACPI_ADD_PTR(struct acpi_pptt_cache_v1, > + cache, > + sizeof(struct acpi_pptt_cache)); sizeof(*cache) to me makes this more obvious. > + > + if (cache->flags & ACPI_PPTT_CACHE_ID_VALID && > + cache_v1->cache_id == cache_id) > + return level; > + } > + } > + > + return -ENOENT; > +}