Subject: Re: [PATCH v6 6/6] powerpc/pseries: Consolidate form1 distance initialization into a helper

From: David Gibson <[email-masked]>
Date: Fri, 6 Aug 2021 16:47:39 +1000

On Tue, Jul 27, 2021 at 03:33:11PM +0530, Aneesh Kumar K.V wrote:
> Currently, we duplicate parsing code for ibm,associativity and
> ibm,associativity-lookup-arrays in the kernel. The associativity array provided
> by these device tree properties are very similar and hence can use
> a helper to parse the node id and numa distance details.

Oh... sorry.. comments on the earlier patch were from before I read
and saw you adjusted things here.

> 
> Signed-off-by: Aneesh Kumar K.V <[email-masked]>
> ---
>  arch/powerpc/mm/numa.c | 83 ++++++++++++++++++++++++++----------------
>  1 file changed, 51 insertions(+), 32 deletions(-)
> 
> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> index fffb3c40f595..7506251e17f2 100644
> --- a/arch/powerpc/mm/numa.c
> +++ b/arch/powerpc/mm/numa.c
> @@ -171,19 +171,19 @@ static void unmap_cpu_from_node(unsigned long cpu)
>  }
>  #endif /* CONFIG_HOTPLUG_CPU || CONFIG_PPC_SPLPAR */
>  
> -/*
> - * Returns nid in the range [0..nr_node_ids], or -1 if no useful NUMA
> - * info is found.
> - */
> -static int associativity_to_nid(const __be32 *associativity)
> +static int __associativity_to_nid(const __be32 *associativity,
> +				  int max_array_sz)
>  {
>  	int nid = NUMA_NO_NODE;
> +	/*
> +	 * primary_domain_index is 1 based array index.
> +	 */
> +	int index = primary_domain_index  - 1;
>  
> -	if (!numa_enabled)
> +	if (!numa_enabled || index >= max_array_sz)
>  		goto out;

You don't need a goto, you can just return NUMA_NO_NODE.

>  
> -	if (of_read_number(associativity, 1) >= primary_domain_index)
> -		nid = of_read_number(&associativity[primary_domain_index], 1);
> +	nid = of_read_number(&associativity[index], 1);
>  
>  	/* POWER4 LPAR uses 0xffff as invalid node */
>  	if (nid == 0xffff || nid >= nr_node_ids)
> @@ -191,6 +191,17 @@ static int associativity_to_nid(const __be32 *associativity)
>  out:
>  	return nid;
>  }
> +/*
> + * Returns nid in the range [0..nr_node_ids], or -1 if no useful NUMA
> + * info is found.
> + */
> +static int associativity_to_nid(const __be32 *associativity)
> +{
> +	int array_sz = of_read_number(associativity, 1);
> +
> +	/* Skip the first element in the associativity array */
> +	return __associativity_to_nid((associativity + 1), array_sz);
> +}
>  
>  static int __cpu_form2_relative_distance(__be32 *cpu1_assoc, __be32 *cpu2_assoc)
>  {
> @@ -295,24 +306,41 @@ int of_node_to_nid(struct device_node *device)
>  }
>  EXPORT_SYMBOL(of_node_to_nid);
>  
> -static void __initialize_form1_numa_distance(const __be32 *associativity)
> +static void ___initialize_form1_numa_distance(const __be32 *associativity,
> +					     int max_array_sz)
>  {
>  	int i, nid;
>  
>  	if (affinity_form != FORM1_AFFINITY)
>  		return;
>  
> -	nid = associativity_to_nid(associativity);
> +	nid = __associativity_to_nid(associativity, max_array_sz);
>  	if (nid != NUMA_NO_NODE) {
>  		for (i = 0; i < distance_ref_points_depth; i++) {
>  			const __be32 *entry;
> +			int index = be32_to_cpu(distance_ref_points[i]) - 1;
> +
> +			/*
> +			 * broken hierarchy, return with broken distance table

WARN_ON, maybe?

> +			 */
> +			if (index >= max_array_sz)
> +				return;
>  
> -			entry = &associativity[be32_to_cpu(distance_ref_points[i])];
> +			entry = &associativity[index];
>  			distance_lookup_table[nid][i] = of_read_number(entry, 1);
>  		}
>  	}
>  }
>  
> +static void __initialize_form1_numa_distance(const __be32 *associativity)

Do you actually use this in-between wrapper?

> +{
> +	int array_sz;
> +
> +	array_sz = of_read_number(associativity, 1);
> +	/* Skip the first element in the associativity array */
> +	___initialize_form1_numa_distance(associativity + 1, array_sz);
> +}
> +
>  static void initialize_form1_numa_distance(struct device_node *node)
>  {
>  	const __be32 *associativity;
> @@ -586,27 +614,18 @@ static int get_nid_and_numa_distance(struct drmem_lmb *lmb)
>  
>  	if (primary_domain_index <= aa.array_sz &&
>  	    !(lmb->flags & DRCONF_MEM_AI_INVALID) && lmb->aa_index < aa.n_arrays) {
> -		index = lmb->aa_index * aa.array_sz + primary_domain_index - 1;
> -		nid = of_read_number(&aa.arrays[index], 1);
> +		const __be32 *associativity;
>  
> -		if (nid == 0xffff || nid >= nr_node_ids)
> -			nid = default_nid;
> +		index = lmb->aa_index * aa.array_sz;
> +		associativity = &aa.arrays[index];
> +		nid = __associativity_to_nid(associativity, aa.array_sz);
>  		if (nid > 0 && affinity_form == FORM1_AFFINITY) {
> -			int i;
> -			const __be32 *associativity;
> -
> -			index = lmb->aa_index * aa.array_sz;
> -			associativity = &aa.arrays[index];
>  			/*
> -			 * lookup array associativity entries have different format
> -			 * There is no length of the array as the first element.
> +			 * lookup array associativity entries have
> +			 * no length of the array as the first element.
>  			 */
> -			for (i = 0; i < distance_ref_points_depth; i++) {
> -				const __be32 *entry;
> -
> -				entry = &associativity[be32_to_cpu(distance_ref_points[i]) - 1];
> -				distance_lookup_table[nid][i] = of_read_number(entry, 1);
> -			}
> +			___initialize_form1_numa_distance(associativity,
> +							  aa.array_sz);

Better, thanks.

>  		}
>  	}
>  	return nid;
> @@ -632,11 +651,11 @@ int of_drconf_to_nid_single(struct drmem_lmb *lmb)
>  
>  	if (primary_domain_index <= aa.array_sz &&
>  	    !(lmb->flags & DRCONF_MEM_AI_INVALID) && lmb->aa_index < aa.n_arrays) {
> -		index = lmb->aa_index * aa.array_sz + primary_domain_index - 1;
> -		nid = of_read_number(&aa.arrays[index], 1);
> +		const __be32 *associativity;
>  
> -		if (nid == 0xffff || nid >= nr_node_ids)
> -			nid = default_nid;
> +		index = lmb->aa_index * aa.array_sz;
> +		associativity = &aa.arrays[index];
> +		nid = __associativity_to_nid(associativity, aa.array_sz);
>  	}
>  	return nid;
>  }

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson