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Message-ID: <e642278d-c594-430c-5a53-31a74f6973e8@linux.ibm.com>
Date: Thu, 29 Apr 2021 14:38:56 +0200
From: Laurent Dufour <ldufour@...ux.ibm.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
mpe@...erman.id.au, benh@...nel.crashing.org, paulus@...ba.org
Cc: nathanl@...ux.ibm.com, Tyrel Datwyler <tyreld@...ux.ibm.com>,
linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] pseries/drmem: update LMBs after LPM
Le 29/04/2021 à 12:27, Aneesh Kumar K.V a écrit :
> Laurent Dufour <ldufour@...ux.ibm.com> writes:
>
>> After a LPM, the device tree node ibm,dynamic-reconfiguration-memory may be
>> updated by the hypervisor in the case the NUMA topology of the LPAR's
>> memory is updated.
>>
>> This is caught by the kernel, but the memory's node is updated because
>> there is no way to move a memory block between nodes.
>>
>> If later a memory block is added or removed, drmem_update_dt() is called
>> and it is overwriting the DT node to match the added or removed LMB. But
>> the LMB's associativity node has not been updated after the DT node update
>> and thus the node is overwritten by the Linux's topology instead of the
>> hypervisor one.
>>
>> Introduce a hook called when the ibm,dynamic-reconfiguration-memory node is
>> updated to force an update of the LMB's associativity.
>>
>> Cc: Tyrel Datwyler <tyreld@...ux.ibm.com>
>> Signed-off-by: Laurent Dufour <ldufour@...ux.ibm.com>
>> ---
>>
>> V3:
>> - Check rd->dn->name instead of rd->dn->full_name
>> V2:
>> - Take Tyrel's idea to rely on OF_RECONFIG_UPDATE_PROPERTY instead of
>> introducing a new hook mechanism.
>> ---
>> arch/powerpc/include/asm/drmem.h | 1 +
>> arch/powerpc/mm/drmem.c | 35 +++++++++++++++++++
>> .../platforms/pseries/hotplug-memory.c | 4 +++
>> 3 files changed, 40 insertions(+)
>>
>> diff --git a/arch/powerpc/include/asm/drmem.h b/arch/powerpc/include/asm/drmem.h
>> index bf2402fed3e0..4265d5e95c2c 100644
>> --- a/arch/powerpc/include/asm/drmem.h
>> +++ b/arch/powerpc/include/asm/drmem.h
>> @@ -111,6 +111,7 @@ int drmem_update_dt(void);
>> int __init
>> walk_drmem_lmbs_early(unsigned long node, void *data,
>> int (*func)(struct drmem_lmb *, const __be32 **, void *));
>> +void drmem_update_lmbs(struct property *prop);
>> #endif
>>
>> static inline void invalidate_lmb_associativity_index(struct drmem_lmb *lmb)
>> diff --git a/arch/powerpc/mm/drmem.c b/arch/powerpc/mm/drmem.c
>> index 9af3832c9d8d..f0a6633132af 100644
>> --- a/arch/powerpc/mm/drmem.c
>> +++ b/arch/powerpc/mm/drmem.c
>> @@ -307,6 +307,41 @@ int __init walk_drmem_lmbs_early(unsigned long node, void *data,
>> return ret;
>> }
>>
>> +/*
>> + * Update the LMB associativity index.
>> + */
>> +static int update_lmb(struct drmem_lmb *updated_lmb,
>> + __maybe_unused const __be32 **usm,
>> + __maybe_unused void *data)
>> +{
>> + struct drmem_lmb *lmb;
>> +
>> + /*
>> + * Brut force there may be better way to fetch the LMB
>> + */
>> + for_each_drmem_lmb(lmb) {
>> + if (lmb->drc_index != updated_lmb->drc_index)
>> + continue;
>> +
>> + lmb->aa_index = updated_lmb->aa_index;
>> + break;
>> + }
>> + return 0;
>> +}
>> +
>> +/*
>> + * Update the LMB associativity index.
>> + *
>> + * This needs to be called when the hypervisor is updating the
>> + * dynamic-reconfiguration-memory node property.
>> + */
>> +void drmem_update_lmbs(struct property *prop)
>> +{
>> + if (!strcmp(prop->name, "ibm,dynamic-memory"))
>> + __walk_drmem_v1_lmbs(prop->value, NULL, NULL, update_lmb);
>> + else if (!strcmp(prop->name, "ibm,dynamic-memory-v2"))
>> + __walk_drmem_v2_lmbs(prop->value, NULL, NULL, update_lmb);
>> +}
>> #endif
>>
>> static int init_drmem_lmb_size(struct device_node *dn)
>> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
>> index 8377f1f7c78e..672ffbee2e78 100644
>> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
>> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
>> @@ -949,6 +949,10 @@ static int pseries_memory_notifier(struct notifier_block *nb,
>> case OF_RECONFIG_DETACH_NODE:
>> err = pseries_remove_mem_node(rd->dn);
>> break;
>> + case OF_RECONFIG_UPDATE_PROPERTY:
>> + if (!strcmp(rd->dn->name,
>> + "ibm,dynamic-reconfiguration-memory"))
>> + drmem_update_lmbs(rd->prop);
>> }
>> return notifier_from_errno(err);
>
> How will this interact with DLPAR memory? When we dlpar memory,
> ibm,configure-connector is used to fetch the new associativity details
> and set drmem_lmb->aa_index correctly there. Once that is done kernel
> then call drmem_update_dt() which will result in the above notifier
> callback?
>
> IIUC, the call back then will update drmem_lmb->aa_index again?
Thanks for pointing this Aneesh,
You're right I missed that callback and it was quite invisible during my test
because the value set back in the aa_index was the same.
When dmrem_update_dt() is called, there is no need to update the LMB back and
the DT modify notifier should be ignored.
As DLPAR operations are serialized (by lock_device_hotplug()), I'm proposing to
rely on a boolean static variable to do skip this notification, like this:
diff --git a/arch/powerpc/mm/drmem.c b/arch/powerpc/mm/drmem.c
index f0a6633132af..3c0130720086 100644
--- a/arch/powerpc/mm/drmem.c
+++ b/arch/powerpc/mm/drmem.c
@@ -18,6 +18,7 @@ static int n_root_addr_cells, n_root_size_cells;
static struct drmem_lmb_info __drmem_info;
struct drmem_lmb_info *drmem_info = &__drmem_info;
+static bool in_drmem_update;
u64 drmem_lmb_memory_max(void)
{
@@ -178,6 +179,11 @@ int drmem_update_dt(void)
if (!memory)
return -1;
+ /*
+ * Set in_drmem_update to prevent the notifier callback to process the
+ * DT property back since the change is coming from the LMB tree.
+ */
+ in_drmem_update = true;
prop = of_find_property(memory, "ibm,dynamic-memory", NULL);
if (prop) {
rc = drmem_update_dt_v1(memory, prop);
@@ -186,6 +192,7 @@ int drmem_update_dt(void)
if (prop)
rc = drmem_update_dt_v2(memory, prop);
}
+ in_drmem_update = false;
of_node_put(memory);
return rc;
@@ -337,6 +344,12 @@ static int update_lmb(struct drmem_lmb *updated_lmb,
*/
void drmem_update_lmbs(struct property *prop)
{
+ /*
+ * Don't update the LMBs If called from the update done in
+ * drmem_update_dt().
+ */
+ if (in_drmem_update)
+ return;
if (!strcmp(prop->name, "ibm,dynamic-memory"))
__walk_drmem_v1_lmbs(prop->value, NULL, NULL, update_lmb);
else if (!strcmp(prop->name, "ibm,dynamic-memory-v2"))
Any concern with this option?
Laurent.
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