On 10/29/18 1:43 PM, Nathan Fontenot wrote:
> On pseries systems, performing a partition migration can result in
> altering the nodes a CPU is assigned to on the destination system. For
> exampl, pre-migration on the source system CPUs are in node 1 and 3,
> post-migration on the destination system CPUs are in nodes 2 and 3.
>
> Handling the node change for a CPU can cause corruption in the slab
> cache if we hit a timing where a CPUs node is changed while cache_reap()
> is invoked. The corruption occurs because the slab cache code appears
> to rely on the CPU and slab cache pages being on the same node.
>
> The current dynamic updating of a CPUs node done in arch/powerpc/mm/numa.c
> does not prevent us from hitting this scenario.
>
> Changing the device tree property update notification handler that
> recognizes an affinity change for a CPU to do a full DLPAR remove and
> add of the CPU instead of dynamically changing its node resolves this
> issue.
>
> Signed-off-by: Nathan Fontenot <nf...@linux.vnet.ibm.com
Signed-off-by: Michael W. Bringmann <m...@linux.vnet.ibm.com>
> ---
> arch/powerpc/include/asm/topology.h | 2 ++
> arch/powerpc/mm/numa.c | 9 +--------
> arch/powerpc/platforms/pseries/hotplug-cpu.c | 19 +++++++++++++++++++
> 3 files changed, 22 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/topology.h
> b/arch/powerpc/include/asm/topology.h
> index a4a718dbfec6..f85e2b01c3df 100644
> --- a/arch/powerpc/include/asm/topology.h
> +++ b/arch/powerpc/include/asm/topology.h
> @@ -132,6 +132,8 @@ static inline void shared_proc_topology_init(void) {}
> #define topology_sibling_cpumask(cpu) (per_cpu(cpu_sibling_map, cpu))
> #define topology_core_cpumask(cpu) (per_cpu(cpu_core_map, cpu))
> #define topology_core_id(cpu) (cpu_to_core_id(cpu))
> +
> +int dlpar_cpu_readd(int cpu);
> #endif
> #endif
>
> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> index 693ae1c1acba..bb6a7b56bef7 100644
> --- a/arch/powerpc/mm/numa.c
> +++ b/arch/powerpc/mm/numa.c
> @@ -1461,13 +1461,6 @@ static void reset_topology_timer(void)
>
> #ifdef CONFIG_SMP
>
> -static void stage_topology_update(int core_id)
> -{
> - cpumask_or(&cpu_associativity_changes_mask,
> - &cpu_associativity_changes_mask, cpu_sibling_mask(core_id));
> - reset_topology_timer();
> -}
> -
> static int dt_update_callback(struct notifier_block *nb,
> unsigned long action, void *data)
> {
> @@ -1480,7 +1473,7 @@ static int dt_update_callback(struct notifier_block *nb,
> !of_prop_cmp(update->prop->name, "ibm,associativity")) {
> u32 core_id;
> of_property_read_u32(update->dn, "reg", &core_id);
> - stage_topology_update(core_id);
> + rc = dlpar_cpu_readd(core_id);
> rc = NOTIFY_OK;
> }
> break;
> diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c
> b/arch/powerpc/platforms/pseries/hotplug-cpu.c
> index 2f8e62163602..97feb6e79f1a 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
> @@ -802,6 +802,25 @@ static int dlpar_cpu_add_by_count(u32 cpus_to_add)
> return rc;
> }
>
> +int dlpar_cpu_readd(int cpu)
> +{
> + struct device_node *dn;
> + struct device *dev;
> + u32 drc_index;
> + int rc;
> +
> + dev = get_cpu_device(cpu);
> + dn = dev->of_node;
> +
> + rc = of_property_read_u32(dn, "ibm,my-drc-index", &drc_index);
> +
> + rc = dlpar_cpu_remove_by_index(drc_index);
> + if (!rc)
> + rc = dlpar_cpu_add(drc_index);
> +
> + return rc;
> +}
> +
> int dlpar_cpu(struct pseries_hp_errorlog *hp_elog)
> {
> u32 count, drc_index;
>
>
--
Michael W. Bringmann
Linux Technology Center
IBM Corporation
Tie-Line 363-5196
External: (512) 286-5196
Cell: (512) 466-0650
m...@linux.vnet.ibm.com
