linux-kernel - Re: [RFC PATCH 08/36] ACPI / PPTT: Add a helper to fill a cpumask from a cache

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Message-ID: <20b39d32-b50e-4ab7-a060-6d7221e9d893@arm.com>
Date: Tue, 5 Aug 2025 18:06:57 +0100
From: James Morse <james.morse@....com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 Rob Herring <robh@...nel.org>, Ben Horgan <ben.horgan@....com>,
 Rohit Mathew <rohit.mathew@....com>,
 Shanker Donthineni <sdonthineni@...dia.com>, Zeng Heng
 <zengheng4@...wei.com>, Lecopzer Chen <lecopzerc@...dia.com>,
 Carl Worth <carl@...amperecomputing.com>,
 shameerali.kolothum.thodi@...wei.com,
 D Scott Phillips OS <scott@...amperecomputing.com>, lcherian@...vell.com,
 bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
 baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
 Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
 dfustini@...libre.com, amitsinght@...vell.com,
 David Hildenbrand <david@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>,
 Dave Martin <dave.martin@....com>, Koba Ko <kobak@...dia.com>,
 Sudeep Holla <sudeep.holla@....com>
Subject: Re: [RFC PATCH 08/36] ACPI / PPTT: Add a helper to fill a cpumask
 from a cache_id

Hi Jonathan,

On 16/07/2025 17:24, Jonathan Cameron wrote:
> On Fri, 11 Jul 2025 18:36:20 +0000
> James Morse <james.morse@....com> 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 f53748a5df19..81f7ac18c023 100644
>> --- a/drivers/acpi/pptt.c
>> +++ b/drivers/acpi/pptt.c
>> @@ -985,3 +985,73 @@ int find_acpi_cache_level_from_id(u32 cache_id)

>> +int acpi_pptt_get_cpumask_from_cache_id(u32 cache_id, cpumask_t *cpus)
>> +{
>> +	u32 acpi_cpu_id;
>> +	acpi_status status;
>> +	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;
>> +
>> +	cpumask_clear(cpus);
>> +
>> +	status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);

> Similar suggestions to previous patch apply here as well.

Done!


> 
>> +	if (ACPI_FAILURE(status)) {
>> +		acpi_pptt_warn_missing();
>> +		return -ENOENT;
>> +	}
>> +
>> +	if (table->revision < 3) {
>> +		acpi_put_table(table);
>> +		return -ENOENT;
>> +	}
>> +
>> +	/*
>> +	 * If we found the cache first, we'd still need to walk from each cpu.
>> +	 */
>> +	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)
>> +			break;
>> +		acpi_count_levels(table, cpu_node, &num_levels, 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);
>> +			}

> Unnecessary {}  Fine to keep them if you add something else here later.

The condition being broken over multiple lines de-rails my C parsing abilities... 'Fixed'.


Thanks,

James