Re: [PATCH v3 2/3] powerpc/pseries: Introduce memory hotplug READD operation

[Nathan Fontenot <nfont@linux.vnet.ibm.com>]

On 01/06/2017 01:27 PM, John Allen wrote:
> Currently, memory must be hot removed and subsequently re-added in order
> to dynamically update the affinity of LMBs specified by a PRRN event.
> Earlier implementations of the PRRN event handler ran into issues in which
> the hot remove would occur successfully, but a hotplug event would be
> initiated from another source and grab the hotplug lock preventing the hot
> add from occurring. To prevent this situation, this patch introduces the
> notion of a hot "readd" action for memory which atomizes a hot remove and
> a hot add into a single, serialized operation on the hotplug queue.
> 
> Signed-off-by: John Allen <jallen@linux.vnet.ibm.com>

Reviewed-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>

> ---
> diff --git a/arch/powerpc/include/asm/rtas.h b/arch/powerpc/include/asm/rtas.h
> index 9c23baa..076b892 100644
> --- a/arch/powerpc/include/asm/rtas.h
> +++ b/arch/powerpc/include/asm/rtas.h
> @@ -318,6 +318,7 @@ struct pseries_hp_errorlog {
> 
>  #define PSERIES_HP_ELOG_ACTION_ADD	1
>  #define PSERIES_HP_ELOG_ACTION_REMOVE	2
> +#define PSERIES_HP_ELOG_ACTION_READD	3
> 
>  #define PSERIES_HP_ELOG_ID_DRC_NAME	1
>  #define PSERIES_HP_ELOG_ID_DRC_INDEX	2
> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
> index 0eb4b1d..06f10a8 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
> @@ -560,6 +560,44 @@ static int dlpar_memory_remove_by_index(u32 drc_index, struct property *prop)
>  	return rc;
>  }
> 
> +static int dlpar_memory_readd_by_index(u32 drc_index, struct property *prop)
> +{
> +	struct of_drconf_cell *lmbs;
> +	u32 num_lmbs, *p;
> +	int lmb_found;
> +	int i, rc;
> +
> +	pr_info("Attempting to update LMB, drc index %x\n", drc_index);
> +
> +	p = prop->value;
> +	num_lmbs = *p++;
> +	lmbs = (struct of_drconf_cell *)p;
> +
> +	lmb_found = 0;
> +	for (i = 0; i < num_lmbs; i++) {
> +		if (lmbs[i].drc_index == drc_index) {
> +			lmb_found = 1;
> +			rc = dlpar_remove_lmb(&lmbs[i]);
> +			if (!rc) {
> +				rc = dlpar_add_lmb(&lmbs[i]);
> +				if (rc)
> +					dlpar_release_drc(lmbs[i].drc_index);
> +			}
> +			break;
> +		}
> +	}
> +
> +	if (!lmb_found)
> +		rc = -EINVAL;
> +
> +	if (rc)
> +		pr_info("Failed to update memory at %llx\n",
> +			lmbs[i].base_addr);
> +	else
> +		pr_info("Memory at %llx was updated\n", lmbs[i].base_addr);
> +
> +	return rc;
> +}
>  #else
>  static inline int pseries_remove_memblock(unsigned long base,
>  					  unsigned int memblock_size)
> @@ -776,6 +814,9 @@ int dlpar_memory(struct pseries_hp_errorlog *hp_elog)
>  		else
>  			rc = -EINVAL;
>  		break;
> +	case PSERIES_HP_ELOG_ACTION_READD:
> +		rc = dlpar_memory_readd_by_index(drc_index, prop);
> +		break;
>  	default:
>  		pr_err("Invalid action (%d) specified\n", hp_elog->action);
>  		rc = -EINVAL;
>