Re: [PATCH] powerpc/mobility: Extend start/stop topology update scope

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

On 10/01/2018 01:56 PM, Michael Bringmann wrote:
> The PPC mobility code may receive RTAS requests to perform PRRN
> topology changes at any time, including during LPAR migration
> operations.  In some configurations where the affinity of CPUs
> or memory is being changed on that platform, the PRRN requests
> may apply or refer to outdated information prior to the complete
> update of the device-tree.  This patch changes the duration for
> which topology updates are suppressed during LPAR migrations from
> just the rtas_ibm_suspend_me / 'ibm,suspend-me' call(s) to cover
> the entire 'migration_store' operation to allow all changes to
> the device-tree to be applied prior to accepting and applying any
> PRRN requests.
> 
> For tracking purposes, pr_info notices are added to the functions
> start_topology_update() and stop_topology_update() of 'numa.c'.
> 
> Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com>

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

> ---
>  arch/powerpc/kernel/rtas.c                |    4 ----
>  arch/powerpc/mm/numa.c                    |    6 ++++++
>  arch/powerpc/platforms/pseries/mobility.c |    5 +++++
>  3 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
> index 8afd146..28d8b57 100644
> --- a/arch/powerpc/kernel/rtas.c
> +++ b/arch/powerpc/kernel/rtas.c
> @@ -981,8 +981,6 @@ int rtas_ibm_suspend_me(u64 handle)
>  		goto out;
>  	}
> 
> -	stop_topology_update();
> -
>  	/* Call function on all CPUs.  One of us will make the
>  	 * rtas call
>  	 */
> @@ -994,8 +992,6 @@ int rtas_ibm_suspend_me(u64 handle)
>  	if (atomic_read(&data.error) != 0)
>  		printk(KERN_ERR "Error doing global join\n");
> 
> -	start_topology_update();
> -
>  	/* Take down CPUs not online prior to suspend */
>  	cpuret = rtas_offline_cpus_mask(offline_mask);
>  	if (cpuret)
> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> index b5a71ba..0ade0a1 100644
> --- a/arch/powerpc/mm/numa.c
> +++ b/arch/powerpc/mm/numa.c
> @@ -1518,6 +1518,10 @@ int start_topology_update(void)
>  		}
>  	}
> 
> +	pr_info("Starting topology update%s%s\n",
> +		(prrn_enabled ? " prrn_enabled" : ""),
> +		(vphn_enabled ? " vphn_enabled" : ""));
> +
>  	return rc;
>  }
> 
> @@ -1539,6 +1543,8 @@ int stop_topology_update(void)
>  		rc = del_timer_sync(&topology_timer);
>  	}
> 
> +	pr_info("Stopping topology update\n");
> +
>  	return rc;
>  }
> 
> diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
> index 23fb9ac..49ebefd 100644
> --- a/arch/powerpc/platforms/pseries/mobility.c
> +++ b/arch/powerpc/platforms/pseries/mobility.c
> @@ -373,6 +373,8 @@ static ssize_t migration_store(struct class *class,
>  	if (rc)
>  		return rc;
> 
> +	stop_topology_update();
> +
>  	do {
>  		rc = rtas_ibm_suspend_me(streamid);
>  		if (rc == -EAGAIN)
> @@ -383,6 +385,9 @@ static ssize_t migration_store(struct class *class,
>  		return rc;
> 
>  	post_mobility_fixup();
> +
> +	start_topology_update();
> +
>  	return count;
>  }
> 
>