[RFC v2 1/3] hotplug/mobility: Apply assoc updates for Post Migration Topo
Nathan Fontenot
nfont at linux.vnet.ibm.com
Fri Apr 27 04:31:59 AEST 2018
On 04/24/2018 04:33 PM, Michael Bringmann wrote:
> See comments below:
>
> On 04/24/2018 11:56 AM, Nathan Fontenot wrote:
>> On 02/26/2018 02:52 PM, Michael Bringmann wrote:
>>> hotplug/mobility: Recognize more changes to the associativity of
>>> memory blocks described by the 'ibm,dynamic-memory' and 'cpu'
>>> properties when processing the topology of LPARS in Post Migration
>>> events. Previous efforts only recognized whether a memory block's
>>> assignment had changed in the property. Changes here include:
>>>
>>> * Checking the aa_index values of the old/new properties and 'readd'
>>> any block for which the setting has changed.
>>> * Checking for changes in cpu associativity and making 'readd' calls
>>> when differences are observed.
>>
>> As part of the post-migration updates do you need to hold a lock
>> so that we don't attempt to process any of the cpu/memory changes
>> while the device tree is being updated?
>>
>> You may be able to grab the device hotplug lock for this.
>
> The CPU Re-add process reuses the dlpar_cpu_remove / dlpar_cpu_add
> code for POWERPC. These functions end up invoking device_online() /
> device_offline() which in turn end up invoking the 'cpus_write_lock/unlock'
> around every kernel change to the CPU structures. It was modeled
> on the Memory Re-add process as we discussed a while back, which
> also uses device_online and a corresponding write lock for each
> LMB processed.
>
> Do you see a need for a coarser granularity of locking around
> all or a group of the cpu/memory changes? The data structures
> that the kernel outside of powerpc uses for CPUs and LMBs seem
> to be quite well isolated from the device-tree properties.
My thinking was for memory and CPU updates, the idea being that all
updates are queued up until after the post-LPM device tree updates happens.
Grabbing the device_hotplug lock while updating the device tree would
prevent any of the queued CPU/memory updates from happening.
>
>>
>>>
>>> Signed-off-by: Michael Bringmann <mwb at linux.vnet.ibm.com>
>>> ---
>>> Changes in RFC:
>>> -- Simplify code to update CPU nodes during mobility checks.
>>> Remove functions to generate extra HP_ELOG messages in favor
>>> of direct function calls to dlpar_cpu_readd_by_index.
>>> -- Move check for "cpu" node type from pseries_update_cpu to
>>> pseries_smp_notifier in 'hotplug-cpu.c'
>>> -- Remove functions 'pseries_memory_readd_by_index' and
>>> 'pseries_cpu_readd_by_index' as no longer needed outside of
>>> 'mobility.c'.
>>> ---
>>> arch/powerpc/platforms/pseries/hotplug-cpu.c | 69 +++++++++++++++++++++++
>>> arch/powerpc/platforms/pseries/hotplug-memory.c | 6 ++
>>> 2 files changed, 75 insertions(+)
>>>
>>> diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
>>> index a7d14aa7..91ef22a 100644
>>> --- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
>>> +++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
>>> @@ -636,6 +636,27 @@ static int dlpar_cpu_remove_by_index(u32 drc_index)
>>> return rc;
>>> }
>>>
>>> +static int dlpar_cpu_readd_by_index(u32 drc_index)
>>> +{
>>> + int rc = 0;
>>> +
>>> + pr_info("Attempting to update CPU, drc index %x\n", drc_index);
>>
>> Should make this say we are re-adding the CPU, it's a bit more specific as
>> to what is really happening.
>
> Okay. I will update the notice from dlpar_memory_readd_by_index, as well.
Looks like your current message mirrors what the memory readd routine has,
let's just keep the message as is.
-Nathan
>>
>>> +
>>> + if (dlpar_cpu_remove_by_index(drc_index))
>>> + rc = -EINVAL;
>>> + else if (dlpar_cpu_add(drc_index))
>>> + rc = -EINVAL;
>>> +
>>> + if (rc)
>>> + pr_info("Failed to update cpu at drc_index %lx\n",
>>> + (unsigned long int)drc_index);
>>> + else
>>> + pr_info("CPU at drc_index %lx was updated\n",
>>> + (unsigned long int)drc_index);
>>> +
>>> + return rc;
>>> +}
>>> +
>>> static int find_dlpar_cpus_to_remove(u32 *cpu_drcs, int cpus_to_remove)
>>> {
>>> struct device_node *dn;
>>> @@ -826,6 +847,9 @@ int dlpar_cpu(struct pseries_hp_errorlog *hp_elog)
>>> else
>>> rc = -EINVAL;
>>> break;
>>> + case PSERIES_HP_ELOG_ACTION_READD:
>>> + rc = dlpar_cpu_readd_by_index(drc_index);
>>> + break;
>>> default:
>>> pr_err("Invalid action (%d) specified\n", hp_elog->action);
>>> rc = -EINVAL;
>>> @@ -876,12 +900,53 @@ static ssize_t dlpar_cpu_release(const char *buf, size_t count)
>>>
>>> #endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
>>>
>>> +static int pseries_update_cpu(struct of_reconfig_data *pr)
>>> +{
>>> + u32 old_entries, new_entries;
>>> + __be32 *p, *old_assoc, *new_assoc;
>>> + int rc = 0;
>>> +
>>> + /* So far, we only handle the 'ibm,associativity' property,
>>> + * here.
>>> + * The first int of the property is the number of domains
>>> + * described. This is followed by an array of level values.
>>> + */
>>> + p = (__be32 *) pr->old_prop->value;
>>> + if (!p)
>>> + return -EINVAL;
>>> + old_entries = be32_to_cpu(*p++);
>>> + old_assoc = p;
>>> +
>>> + p = (__be32 *)pr->prop->value;
>>> + if (!p)
>>> + return -EINVAL;
>>> + new_entries = be32_to_cpu(*p++);
>>> + new_assoc = p;
>>> +
>>> + if (old_entries == new_entries) {
>>> + int sz = old_entries * sizeof(int);
>>> +
>>> + if (!memcmp(old_assoc, new_assoc, sz))
>>> + rc = dlpar_cpu_readd_by_index(
>>> + be32_to_cpu(pr->dn->phandle));
>>> +
>>> + } else {
>>> + rc = dlpar_cpu_readd_by_index(
>>> + be32_to_cpu(pr->dn->phandle));
>>> + }
>>> +
>>> + return rc;
>>> +}
>>
>> Do we need to do the full compare of the new vs. the old affinity property?
>>
>> I would think we would only get an updated property if the property changes.
>> We don't care what changes in the property at this point, only that it changed.
>> You could just call dlpar_cpu_readd_by_index() directly.
>
> Okay.
>
>>
>> -Nathan
>
> Thanks.
> Michael
>
>>
>>> +
>>> static int pseries_smp_notifier(struct notifier_block *nb,
>>> unsigned long action, void *data)
>>> {
>>> struct of_reconfig_data *rd = data;
>>> int err = 0;
>>>
>>> + if (strcmp(rd->dn->type, "cpu"))
>>> + return notifier_from_errno(err);
>>> +
>>> switch (action) {
>>> case OF_RECONFIG_ATTACH_NODE:
>>> err = pseries_add_processor(rd->dn);
>>> @@ -889,6 +954,10 @@ static int pseries_smp_notifier(struct notifier_block *nb,
>>> case OF_RECONFIG_DETACH_NODE:
>>> pseries_remove_processor(rd->dn);
>>> break;
>>> + case OF_RECONFIG_UPDATE_PROPERTY:
>>> + if (!strcmp(rd->prop->name, "ibm,associativity"))
>>> + err = pseries_update_cpu(rd);
>>> + break;
>>> }
>>> return notifier_from_errno(err);
>>> }
>>> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
>>> index c1578f5..2341eae 100644
>>> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
>>> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
>>> @@ -1040,6 +1040,12 @@ static int pseries_update_drconf_memory(struct of_reconfig_data *pr)
>>> memblock_size);
>>> rc = (rc < 0) ? -EINVAL : 0;
>>> break;
>>> + } else if ((be32_to_cpu(old_drmem[i].aa_index) !=
>>> + be32_to_cpu(new_drmem[i].aa_index)) &&
>>> + (be32_to_cpu(new_drmem[i].flags) &
>>> + DRCONF_MEM_ASSIGNED)) {
>>> + rc = dlpar_memory_readd_by_index(
>>> + be32_to_cpu(new_drmem[i].drc_index))> }
>>> }
>>> return rc;
>>>
>>
>
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