Re: [RFC PATCH v1 18/21] ARM: NUMA: update node_distance with ACPI support

[Julien Grall <julien.grall@arm.com>]

Hello Vijay,

On 09/02/17 15:57, vijay.kilari@gmail.com wrote:
> From: Vijaya Kumar K <Vijaya.Kumar@cavium.com>
>
> Update node_distance() function to handle
> ACPI SLIT table information.
>
> Signed-off-by: Vijaya Kumar <Vijaya.Kumar@cavium.com>
> ---
>  xen/arch/arm/numa.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/xen/arch/arm/numa.c b/xen/arch/arm/numa.c
> index 5c49347..50c3dea 100644
> --- a/xen/arch/arm/numa.c
> +++ b/xen/arch/arm/numa.c
> @@ -23,6 +23,7 @@
>  #include <xen/acpi.h>
>  #include <asm/mm.h>
>  #include <xen/numa.h>
> +#include <xen/srat.h>
>  #include <asm/acpi.h>
>  #include <xen/errno.h>
>  #include <xen/cpumask.h>
> @@ -35,6 +36,7 @@ extern struct node nodes[MAX_NUMNODES] __initdata;
>  extern int num_node_memblks;
>  extern struct node node_memblk_range[NR_NODE_MEMBLKS];
>  extern nodeid_t memblk_nodeid[NR_NODE_MEMBLKS];
> +extern struct acpi_table_slit *__read_mostly acpi_slit;
>
>  void __init numa_set_cpu_node(int cpu, unsigned long hwid)
>  {
> @@ -50,9 +52,24 @@ void __init numa_set_cpu_node(int cpu, unsigned long hwid)
>
>  u8 __node_distance(nodeid_t a, nodeid_t b)
>  {
> -    if ( !node_distance )
> +    unsigned index;
> +    u8 slit_val;
> +
> +    if ( !node_distance && !acpi_slit )
>          return a == b ? 10 : 20;
>
> +    if ( acpi_slit )
> +    {
> +        index = acpi_slit->locality_count * node_to_pxm(a);
> +        slit_val = acpi_slit->entry[index + node_to_pxm(b)];
> +
> +        /* ACPI defines 0xff as an unreachable node and 0-9 are undefined */
> +        if ( (slit_val == 0xff) || (slit_val <= 9) )
> +            return NUMA_NO_DISTANCE;
> +        else
> +            return slit_val;
> +    }
> +

arm/numa.c is the generic code and should not contain any ACPI specific 
code.

But as I said, the way to get the distance on ACPI is the same on x86 
and ARM.

So I would introduce __node_distance callback that will be setup at 
boot-time to either point to the ACPI version or DT version.

Regards,

-- 
Julien Grall

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