Re: [PATCH v2] irqchip/gic-v3-its: Allow GIC ITS number more than MAX_NUMNODES

[John Garry]

On 22/07/2017 04:54, Hanjun Guo wrote:
> From: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
>
> When running 4.13-rc1 on top of D05, I got the boot log:
>
> [    0.000000] SRAT: PXM 0 -> ITS 0 -> Node 0
> [    0.000000] SRAT: PXM 0 -> ITS 1 -> Node 0
> [    0.000000] SRAT: PXM 0 -> ITS 2 -> Node 0
> [    0.000000] SRAT: PXM 1 -> ITS 3 -> Node 1
> [    0.000000] SRAT: ITS affinity exceeding max count[4]
>
> This is wrong on D05 as we have 8 ITSes with 4 NUMA nodes.
>
> So dynamically alloc the memory needed instead of using
> its_srat_maps[MAX_NUMNODES], which count the number of
> ITS entry(ies) in SRAT and alloc its_srat_maps as needed,
> then build the mapping of numa node to ITS ID. Of course,
> its_srat_maps will be freed after ITS probing because
> we don't need that after boot.
>
> After doing this, I got what I wanted:
>
> [    0.000000] SRAT: PXM 0 -> ITS 0 -> Node 0
> [    0.000000] SRAT: PXM 0 -> ITS 1 -> Node 0
> [    0.000000] SRAT: PXM 0 -> ITS 2 -> Node 0
> [    0.000000] SRAT: PXM 1 -> ITS 3 -> Node 1
> [    0.000000] SRAT: PXM 2 -> ITS 4 -> Node 2
> [    0.000000] SRAT: PXM 2 -> ITS 5 -> Node 2
> [    0.000000] SRAT: PXM 2 -> ITS 6 -> Node 2
> [    0.000000] SRAT: PXM 3 -> ITS 7 -> Node 3
>
> Fixes: dbd2b8267233 ("irqchip/gic-v3-its: Add ACPI NUMA node mapping")
> Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
> Cc: Ganapatrao Kulkarni <ganapatrao.kulkarni@xxxxxxxxxx>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
>
> v1->v2:
>   - Add NULL check in acpi_get_its_numa_node() for no ITS affinity case;
>   - Free the its_srat_maps after ITS probing.
>
>  drivers/irqchip/irq-gic-v3-its.c | 39 ++++++++++++++++++++++++++++++++-------
>  1 file changed, 32 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 3ccdf76..1d692aa 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -1847,13 +1847,16 @@ struct its_srat_map {
>  	u32	its_id;
>  };
>
> -static struct its_srat_map its_srat_maps[MAX_NUMNODES] __initdata;
> +static struct its_srat_map *its_srat_maps __initdata;
>  static int its_in_srat __initdata;
>
>  static int __init acpi_get_its_numa_node(u32 its_id)
>  {
>  	int i;
>
> +	if (!its_srat_maps)
> +		return NUMA_NO_NODE;

Question: Does !its_srat_maps always imply its_in_srat == 0, so we could 
just fall through the for loop and return NUMA_NO_NODE without this check?

Or should we be safe/explicit/or falling through loops is a bad coding 
style?

Cheers,
John

> +
>  	for (i = 0; i < its_in_srat; i++) {
>  		if (its_id == its_srat_maps[i].its_id)
>  			return its_srat_maps[i].numa_node;
> @@ -1861,6 +1864,12 @@ static int __init acpi_get_its_numa_node(u32 its_id)
>  	return NUMA_NO_NODE;
>  }
>
> +static int __init gic_acpi_match_srat_its(struct acpi_subtable_header *header,
> +					  const unsigned long end)
> +{
> +	return 0;
> +}
> +
>  static int __init gic_acpi_parse_srat_its(struct acpi_subtable_header *header,
>  			 const unsigned long end)
>  {
> @@ -1877,12 +1886,6 @@ static int __init gic_acpi_parse_srat_its(struct acpi_subtable_header *header,
>  		return -EINVAL;
>  	}
>
> -	if (its_in_srat >= MAX_NUMNODES) {
> -		pr_err("SRAT: ITS affinity exceeding max count[%d]\n",
> -				MAX_NUMNODES);
> -		return -EINVAL;
> -	}
> -
>  	node = acpi_map_pxm_to_node(its_affinity->proximity_domain);
>
>  	if (node == NUMA_NO_NODE || node >= MAX_NUMNODES) {
> @@ -1901,14 +1904,35 @@ static int __init gic_acpi_parse_srat_its(struct acpi_subtable_header *header,
>
>  static void __init acpi_table_parse_srat_its(void)
>  {
> +	int count;
> +
> +	count = acpi_table_parse_entries(ACPI_SIG_SRAT,
> +			sizeof(struct acpi_table_srat),
> +			ACPI_SRAT_TYPE_GIC_ITS_AFFINITY,
> +			gic_acpi_match_srat_its, 0);
> +	if (count <= 0)
> +		return;
> +
> +	its_srat_maps = kmalloc(count * sizeof(struct its_srat_map),
> +				GFP_KERNEL);
> +	if (!its_srat_maps)
> +		return;
> +
>  	acpi_table_parse_entries(ACPI_SIG_SRAT,
>  			sizeof(struct acpi_table_srat),
>  			ACPI_SRAT_TYPE_GIC_ITS_AFFINITY,
>  			gic_acpi_parse_srat_its, 0);
>  }
> +
> +/* free the its_srat_maps after ITS probing */
> +static void __init acpi_its_srat_maps_free(void)
> +{
> +	kfree(its_srat_maps);
> +}
>  #else
>  static void __init acpi_table_parse_srat_its(void)	{ }
>  static int __init acpi_get_its_numa_node(u32 its_id) { return NUMA_NO_NODE; }
> +static void __init acpi_its_srat_maps_free(void) { }
>  #endif
>
>  static int __init gic_acpi_parse_madt_its(struct acpi_subtable_header *header,
> @@ -1955,6 +1979,7 @@ static void __init its_acpi_probe(void)
>  	acpi_table_parse_srat_its();
>  	acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_TRANSLATOR,
>  			      gic_acpi_parse_madt_its, 0);
> +	acpi_its_srat_maps_free();
>  }
>  #else
>  static void __init its_acpi_probe(void) { }