Re: [patch] x86_64: fix cpu_to_node setup for sparse apic_ids

[Andrew Morton]

Ravikiran G Thirumalai <kiran@xxxxxxxxxxxx> wrote:
>
> While booting with SMT disabled in bios, when using acpi srat to setup
> cpu_to_node[],  sparse apic_ids create problems.  Here's a fix for that.
> 

Again, I don't have enough info here to judge the urgency of this patch.

What are the consequences and risks of not having this patch in 2.6.13, and
to how many machines?

> 
> Index: linux-2.6.13-rc3/arch/x86_64/mm/srat.c
> ===================================================================
> --- linux-2.6.13-rc3.orig/arch/x86_64/mm/srat.c	2005-06-17 12:48:29.000000000 -0700
> +++ linux-2.6.13-rc3/arch/x86_64/mm/srat.c	2005-07-27 15:36:23.000000000 -0700
> @@ -20,6 +20,9 @@
>  
>  static struct acpi_table_slit *acpi_slit;
>  
> +/* Internal processor count */
> +static unsigned int __initdata num_processors = 0;
> +
>  static nodemask_t nodes_parsed __initdata;
>  static nodemask_t nodes_found __initdata;
>  static struct node nodes[MAX_NUMNODES] __initdata;
> @@ -101,16 +104,18 @@
>  		bad_srat();
>  		return;
>  	}
> -	if (pa->apic_id >= NR_CPUS) {
> -		printk(KERN_ERR "SRAT: lapic %u too large.\n",
> -		       pa->apic_id);
> +	if (num_processors >= NR_CPUS) {
> +		printk(KERN_ERR "SRAT: Processor #%d (lapic %u) INVALID. (Max ID: %d).\n",
> +			num_processors, pa->apic_id, NR_CPUS);
>  		bad_srat();
>  		return;
>  	}
> -	cpu_to_node[pa->apic_id] = node;
> +	cpu_to_node[num_processors] = node;
>  	acpi_numa = 1;
> -	printk(KERN_INFO "SRAT: PXM %u -> APIC %u -> Node %u\n",
> -	       pxm, pa->apic_id, node);
> +	printk(KERN_INFO "SRAT: PXM %u -> APIC %u -> CPU %u -> Node %u\n",
> +	       pxm, pa->apic_id, num_processors, node);
> +
> +	num_processors++;
>  }
>  
>  /* Callback for parsing of the Proximity Domain <-> Memory Area mappings */
-
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