Re: [PATCH v2 10/10] xen/x86: add detection of memory interleaves for different nodes

[Jan Beulich <jbeulich@xxxxxxxx>]

On 18.04.2022 11:07, Wei Chen wrote:
> --- a/xen/arch/x86/srat.c
> +++ b/xen/arch/x86/srat.c
> @@ -271,6 +271,35 @@ acpi_numa_processor_affinity_init(const struct 
> acpi_srat_cpu_affinity *pa)
>                      pxm, pa->apic_id, node);
>  }
>  
> +/*
> + * Check to see if there are other nodes within this node's range.
> + * We just need to check full contains situation. Because overlaps
> + * have been checked before by conflicting_memblks.
> + */
> +static bool __init check_node_memory_interleave(nodeid_t nid,
> +                                                paddr_t start, paddr_t end)
> +{
> +     nodeid_t i;
> +     const struct node *nd = &nodes[nid];
> +
> +     for_each_node_mask(i, memory_nodes_parsed)
> +     {
> +             /* Skip itself */
> +             if (i == nid)
> +                     continue;
> +
> +             nd = &nodes[i];
> +             if (start < nd->start && nd->end < end) {
> +                     printk(KERN_ERR
> +                            "Node %u: (%"PRIpaddr"-%"PRIpaddr") interleaves 
> with node %u (%"PRIpaddr"-%"PRIpaddr")\n",
> +                            nid, start, end, i, nd->start, nd->end);
> +                     return true;
> +             }
> +     }
> +
> +     return false;
> +}
> +
>  /* Callback for parsing of the Proximity Domain <-> Memory Area mappings */
>  void __init
>  acpi_numa_memory_affinity_init(const struct acpi_srat_mem_affinity *ma)
> @@ -340,10 +369,22 @@ acpi_numa_memory_affinity_init(const struct 
> acpi_srat_mem_affinity *ma)

Just up from here there already is overlap detection (via a call to
conflicting_memblks(), and you even mention that in the earlier
comment). If that doesn't cover all cases, I think it wants fixing
there rather than introducing a 2nd checking function. But afaics
that code covers the "fully contains" case.

Jan

>                       nd->start = start;
>                       nd->end = end;
>               } else {
> -                     if (start < nd->start)
> -                             nd->start = start;
> -                     if (nd->end < end)
> -                             nd->end = end;
> +                     paddr_t new_start = nd->start;
> +                     paddr_t new_end = nd->end;
> +
> +                     if (start < new_start)
> +                             new_start = start;
> +                     if (new_end < end)
> +                             new_end = end;
> +
> +                     /* Check whether new range contains memory for other 
> nodes */
> +                     if (check_node_memory_interleave(node, new_start, 
> new_end)) {
> +                             bad_srat();
> +                             return;
> +                     }
> +
> +                     nd->start = new_start;
> +                     nd->end = new_end;
>               }
>       }
>       printk(KERN_INFO "SRAT: Node %u PXM %u %"PRIpaddr"-%"PRIpaddr"%s\n",