linux-kernel - Re: [PATCH v3 2/2] ACPI/PPTT: Handle architecturally unknown cache types

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Message-ID: <20181002105705.GB1086@e107155-lin>
Date:   Tue, 2 Oct 2018 11:57:05 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Jeffrey Hugo <jhugo@...eaurora.org>
Cc:     gregkh@...uxfoundation.org, rjw@...ysocki.net,
        linux-acpi@...r.kernel.org, jeremy.linton@....com,
        linux-kernel@...r.kernel.org, vkilari@...eaurora.org,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH v3 2/2] ACPI/PPTT: Handle architecturally unknown cache
 types

On Thu, Sep 27, 2018 at 08:57:57PM -0600, Jeffrey Hugo wrote:
> The type of a cache might not be specified by architectural mechanisms (ie
> system registers), but its type might be specified in the PPTT.  In this
> case, we should populate the type of the cache, rather than leave it
> undefined.
> 
> This fixes the issue where the cacheinfo driver will not populate sysfs
> for such caches, resulting in the information missing from utilities like
> lstopo and lscpu, thus degrading the user experience.
> 
> Fixes: 2bd00bcd73e5 (ACPI/PPTT: Add Processor Properties Topology Table parsing)
> Reported-by: Vijaya Kumar K <vkilari@...eaurora.org>
> Signed-off-by: Jeffrey Hugo <jhugo@...eaurora.org>
> ---
>  drivers/acpi/pptt.c | 30 +++++++++++++-----------------
>  1 file changed, 13 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> index d1e26cb..38ac30e 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c
> @@ -357,25 +357,15 @@ static void update_cache_properties(struct cacheinfo *this_leaf,
>  				    struct acpi_pptt_cache *found_cache,
>  				    struct acpi_pptt_processor *cpu_node)
>  {
> -	int valid_flags = 0;
> -
>  	this_leaf->fw_token = cpu_node;
> -	if (found_cache->flags & ACPI_PPTT_SIZE_PROPERTY_VALID) {
> +	if (found_cache->flags & ACPI_PPTT_SIZE_PROPERTY_VALID)
>  		this_leaf->size = found_cache->size;
> -		valid_flags++;
> -	}
> -	if (found_cache->flags & ACPI_PPTT_LINE_SIZE_VALID) {
> +	if (found_cache->flags & ACPI_PPTT_LINE_SIZE_VALID)
>  		this_leaf->coherency_line_size = found_cache->line_size;
> -		valid_flags++;
> -	}
> -	if (found_cache->flags & ACPI_PPTT_NUMBER_OF_SETS_VALID) {
> +	if (found_cache->flags & ACPI_PPTT_NUMBER_OF_SETS_VALID)
>  		this_leaf->number_of_sets = found_cache->number_of_sets;
> -		valid_flags++;
> -	}
> -	if (found_cache->flags & ACPI_PPTT_ASSOCIATIVITY_VALID) {
> +	if (found_cache->flags & ACPI_PPTT_ASSOCIATIVITY_VALID)
>  		this_leaf->ways_of_associativity = found_cache->associativity;
> -		valid_flags++;
> -	}
>  	if (found_cache->flags & ACPI_PPTT_WRITE_POLICY_VALID) {
>  		switch (found_cache->attributes & ACPI_PPTT_MASK_WRITE_POLICY) {
>  		case ACPI_PPTT_CACHE_POLICY_WT:
> @@ -402,11 +392,17 @@ static void update_cache_properties(struct cacheinfo *this_leaf,
>  		}
>  	}
>  	/*
> -	 * If the above flags are valid, and the cache type is NOCACHE
> -	 * update the cache type as well.
> +	 * If cache type is NOCACHE, then the cache hasn't been specified
> +	 * via other mechanisms.  Update the type if a cache type has been
> +	 * provided.
> +	 *
> +	 * Note, we assume such caches are unified based on conventional system
> +	 * design and known examples.  Significant work is required elsewhere to
> +	 * fully support data/instruction only type caches which are only
> +	 * specified in PPTT.
>  	 */
>  	if (this_leaf->type == CACHE_TYPE_NOCACHE &&
> -	    valid_flags == PPTT_CHECKED_ATTRIBUTES)

I don't think we use PPTT_CHECKED_ATTRIBUTES elsewhere.
If so, can we drop that ?

Other than that:
Reviewed-by: Sudeep Holla <sudeep.holla@....com>

--
Regards,
Sudeep