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From: Nathan Lynch <nathanl@linux.ibm.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org,
	Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Subject: Re: [RFC PATCH 1/2] powerpc/numa: Introduce logical numa id
Date: Thu, 06 Aug 2020 23:24:58 -0500
Message-ID: <87pn83ytet.fsf@linux.ibm.com> (raw)
In-Reply-To: <20200731111916.243569-1-aneesh.kumar@linux.ibm.com>

"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> writes:
> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> index e437a9ac4956..6c659aada55b 100644
> --- a/arch/powerpc/mm/numa.c
> +++ b/arch/powerpc/mm/numa.c
> @@ -221,25 +221,51 @@ static void initialize_distance_lookup_table(int nid,
>  	}
>  }
>  
> +static u32 nid_map[MAX_NUMNODES] = {[0 ... MAX_NUMNODES - 1] =  NUMA_NO_NODE};

It's odd to me to use MAX_NUMNODES for this array when it's going to be
indexed not by Linux's logical node IDs but by the platform-provided
domain number, which has no relation to MAX_NUMNODES.

> +
> +int firmware_group_id_to_nid(int firmware_gid)
> +{
> +	static int last_nid = 0;
> +
> +	/*
> +	 * For PowerNV we don't change the node id. This helps to avoid
> +	 * confusion w.r.t the expected node ids. On pseries, node numbers
> +	 * are virtualized. Hence do logical node id for pseries.
> +	 */
> +	if (!firmware_has_feature(FW_FEATURE_LPAR))
> +		return firmware_gid;
> +
> +	if (firmware_gid ==  -1)
> +		return NUMA_NO_NODE;
> +
> +	if (nid_map[firmware_gid] == NUMA_NO_NODE)
> +		nid_map[firmware_gid] = last_nid++;

This should at least be bounds-checked in case of domain numbering in
excess of MAX_NUMNODES. Or a different data structure should be used?
Not sure.

I'd prefer Linux's logical node type not be easily interchangeable with
the firmware node/group id type. The firmware type could be something
like:

struct affinity_domain {
	u32 val;
};
typedef struct affinity_domain affinity_domain_t;

with appropriate accessors/APIs.

This can prevent a whole class of errors that is currently possible with
CPUs, since the logical and "hardware" ID types are both simple
integers.

  parent reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-31 11:19 Aneesh Kumar K.V
2020-07-31 11:22 ` [RFC PATCH 2/2] powerpc/powernv/cpufreq: Don't assume chip id is same as Linux node id Aneesh Kumar K.V
2020-08-04  7:47   ` Gautham R Shenoy
2020-08-01  5:20 ` [RFC PATCH 1/2] powerpc/numa: Introduce logical numa id Srikar Dronamraju
2020-08-02 14:21   ` Aneesh Kumar K.V
2020-08-04  7:25     ` Srikar Dronamraju
2020-08-06 10:44       ` Aneesh Kumar K.V
2020-08-10  8:05         ` Srikar Dronamraju
2020-08-07  4:24 ` Nathan Lynch [this message]
2020-08-07  5:02   ` Aneesh Kumar K.V
2020-08-07 20:45     ` Nathan Lynch
2020-08-09 14:12       ` Aneesh Kumar K.V
2020-08-09 18:40         ` Aneesh Kumar K.V
2020-08-13 22:53           ` Nathan Lynch

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