From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2FD0F8F7D; Thu, 11 Sep 2025 10:59:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.176.79.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757588395; cv=none; b=WUYSIK5y8NreIQXssRfXY6KMgVa++CIlHgkEhTOIJlgJ6ZyFci/0wPEiQi3qVhrbm8vvoN2llhpAXh64WjDK87k2CIIzNGxrBzuzw2tDVcdrsMGDRNKm5i5I6V0qQf7MUj6cQvyyUZrMMStDs+zU45eFNrGmpigYLIFpOom7hs0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757588395; c=relaxed/simple; bh=uZoqkvm+q5Ij6a+vJeqWZwm5rCDuZBdNu42YjXAYRrQ=; h=Date:From:To:CC:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=W/d8FPG8DxzekfLkPbPED1/mWn7Zm+B0UorRGYE5McJwYH+sa2sI8DZDSpoh161Ri9PNWpZYZiy/j6VN93Tf+oCeN0RuXe6QGRWbhL2P0ojwCFzDKa5Ne/DZ41H8+o+FQa+I1JkMpUOsv8llqXdz36LdBYtZjIYG1sipPYf46MY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=185.176.79.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com 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) Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: lhrpeml100012.china.huawei.com (7.191.174.184) To frapeml500008.china.huawei.com (7.182.85.71) 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; > +}