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Received: from foss.arm.com ([217.140.110.172]) by desiato.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v7GPQ-00000002JNm-0soX for linux-arm-kernel@lists.infradead.org; Fri, 10 Oct 2025 16:56:02 +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 04812153B; Fri, 10 Oct 2025 09:55:49 -0700 (PDT) Received: from [10.1.197.69] (eglon.cambridge.arm.com [10.1.197.69]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9FEA73F66E; Fri, 10 Oct 2025 09:55:51 -0700 (PDT) Message-ID: <7dbd9fd8-762b-405b-bb4e-f6adb60c8d80@arm.com> Date: Fri, 10 Oct 2025 17:55:49 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 04/29] ACPI / PPTT: Add a helper to fill a cpumask from a cache_id To: Fenghua Yu , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org Cc: D Scott Phillips OS , carl@os.amperecomputing.com, 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 , Dave Martin , Koba Ko , Shanker Donthineni , baisheng.gao@unisoc.com, Jonathan Cameron , Rob Herring , Rohit Mathew , Rafael Wysocki , Len Brown , Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Catalin Marinas , Will Deacon , Greg Kroah-Hartman , Danilo Krummrich References: <20250910204309.20751-1-james.morse@arm.com> <20250910204309.20751-5-james.morse@arm.com> <094cc278-d488-4d22-a1f4-73616f4b99d5@nvidia.com> Content-Language: en-GB From: James Morse In-Reply-To: <094cc278-d488-4d22-a1f4-73616f4b99d5@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251010_175600_609902_9AA19B95 X-CRM114-Status: GOOD ( 25.87 ) 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 Fenghua, On 02/10/2025 06:03, Fenghua Yu wrote: > On 9/10/25 13:42, James Morse wrote: >> MPAM identifies CPUs by the cache_id in the PPTT cache structure. >> >> The driver needs to know which CPUs are associated with the cache. >> The CPUs may not all be online, so cacheinfo does not have the >> information. >> >> Add a helper to pull this information out of the PPTT. >> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c >> index c5f2a51d280b..c379a9952b00 100644 >> --- a/drivers/acpi/pptt.c >> +++ b/drivers/acpi/pptt.c >> @@ -966,3 +966,62 @@ int find_acpi_cache_level_from_id(u32 cache_id) >> +/** >> + * acpi_pptt_get_cpumask_from_cache_id() - Get the cpus associated with the >> + *                       specified cache >> + * @cache_id: The id field of the unified cache >> + * @cpus: Where to build the cpumask >> + * >> + * Determine which CPUs are below this cache in the PPTT. This allows the property >> + * to be found even if the CPUs are offline. >> + * >> + * The PPTT table must be rev 3 or later, >> + * >> + * Return: -ENOENT if the PPTT doesn't exist, or the cache cannot be found. >> + * Otherwise returns 0 and sets the cpus in the provided cpumask. >> + */ >> +int acpi_pptt_get_cpumask_from_cache_id(u32 cache_id, cpumask_t *cpus) >> +{ >> +    u32 acpi_cpu_id; >> +    int level, cpu, num_levels; >> +    struct acpi_pptt_cache *cache; >> +    struct acpi_pptt_cache_v1 *cache_v1; >> +    struct acpi_pptt_processor *cpu_node; >> +    struct acpi_table_header *table __free(acpi_table) = >> acpi_get_table_ret(ACPI_SIG_PPTT, 0); >> + >> +    cpumask_clear(cpus); >> + >> +    if (IS_ERR(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 (WARN_ON_ONCE(!cpu_node)) >> +            continue; >> +        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)); >> + >> +            if (cache->flags & ACPI_PPTT_CACHE_ID_VALID && >> +                cache_v1->cache_id == cache_id) >> +                cpumask_set_cpu(cpu, cpus); > > This function is almost identical to find_acpi_cache_level_from_id() defined in patch #3. Yes - there is already a lot of repetition in this file. I'd previously suggested to Jeremy L to ahve a walker with callbacks, but he felt that made it harder to read. Jonathan suggested a for_each_acpi_pptt_entry() helper: https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git/commit/?h=pptt/for_each_pptt_entry/v0&id=353ceeba3d39c6b6a10eeb1a59c49649cdf719d8 I'm avoiding including that here as its ~30 patches already! > To reduce code size and complexity, it's better to define a common helper to server both > of the two functions. > > e.g. define a helper acpi_pptt_get_level_cpumask_from_cache_id(u32 cache_id, int *lvl, > cpu_mask_t *cpus) > > This helper has the same code body to traverse the cache levels for all CPUs as > find_acpi_cache_level_from_id() and acpi_pptt_get_cpumask_from_cache_id(). The major > difference is here: > > +            if (cache->flags & ACPI_PPTT_CACHE_ID_VALID && > +                cache_v1->cache_id == cache_id) { > +                if (cpus) > +                    cpumask_set_cpu(cpu, cpus); > +                if ((level) { > +                    *lvl = level; > +                    return 0; > +                } > > Then simplify the two callers as follows: > int find_acpi_cache_level_from_id(u32 cache_id) > { >     int level; >     int err = acpi_pptt_get_level_cpumask_from_cache_id(cache_id, &level, NULL); >     if (err) >         return err; > >     return level; > } > > int acpi_pptt_get_cpumask_from_cache_id(u32 cache_id, cpumask_t *cpus) > { >     return acpi_pptt_get_level_cpumask_from_cache_id(cache_id, NULL, cpus); > } > You've combined two functions that both walk the table (there are quiet a few more in this file) - but they look for very different things. Your common helper is going to be much more complex than either of these standalone. I think Jonathan's for-each helper is the best path forward, that reduces the boiler plate leaving the relevant differences. Thanks, James