[PATCH 2/2] hotplug-cpu.c: set UNISOLATE on dlpar_cpu_remove() failure

[David Gibson]

On Fri, Apr 16, 2021 at 06:02:16PM -0300, Daniel Henrique Barboza wrote:
> The RTAS set-indicator call, when attempting to UNISOLATE a DRC that is
> already UNISOLATED or CONFIGURED, returns RTAS_OK and does nothing else
> for both QEMU and phyp. This gives us an opportunity to use this
> behavior to signal the hypervisor layer when an error during device
> removal happens, allowing it to do a proper error handling, while not
> breaking QEMU/phyp implementations that don't have this support.
> 
> This patch introduces this idea by unisolating all CPU DRCs that failed
> to be removed by dlpar_cpu_remove_by_index(), when handling the
> PSERIES_HP_ELOG_ID_DRC_INDEX event. This is being done for this event
> only because its the only CPU removal event QEMU uses, and there's no
> need at this moment to add this mechanism for phyp only code.
> 
> Signed-off-by: Daniel Henrique Barboza <danielhb413 at gmail.com>

Reviewed-by: David Gibson <david at gibson.dropbear.id.au>

except...

> ---
>  arch/powerpc/platforms/pseries/hotplug-cpu.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
> index 12cbffd3c2e3..ed66895c2f51 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
> @@ -802,8 +802,15 @@ int dlpar_cpu(struct pseries_hp_errorlog *hp_elog)
>  	case PSERIES_HP_ELOG_ACTION_REMOVE:
>  		if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_COUNT)
>  			rc = dlpar_cpu_remove_by_count(count);
> -		else if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX)
> +		else if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX) {
>  			rc = dlpar_cpu_remove_by_index(drc_index);
> +			/* Setting the isolation state of an UNISOLATED/CONFIGURED
> +			 * device to UNISOLATE is a no-op, but the hypervison can

typo here s/hypervison/hypervisor/

> +			 * use it as a hint that the cpu removal failed.
> +			 */
> +			if (rc)
> +				dlpar_unisolate_drc(drc_index);
> +		}
>  		else
>  			rc = -EINVAL;
>  		break;

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
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