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SubjectRe: [PATCH] pseries/drmem: update LMBs after LPM
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On 4/27/21 8:01 AM, Laurent Dufour wrote:
> 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.
>
> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
> ---
> arch/powerpc/include/asm/drmem.h | 1 +
> arch/powerpc/mm/drmem.c | 48 +++++++++++++++++++++++
> arch/powerpc/platforms/pseries/mobility.c | 9 +++++
> 3 files changed, 58 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/drmem.h b/arch/powerpc/include/asm/drmem.h
> index bf2402fed3e0..55c2c25085b0 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(void);
> #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..46074bdfdb3c 100644
> --- a/arch/powerpc/mm/drmem.c
> +++ b/arch/powerpc/mm/drmem.c
> @@ -307,6 +307,54 @@ 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(void)
> +{
> + struct device_node *node;
> + const __be32 *prop;
> +
> + node = of_find_node_by_path("/ibm,dynamic-reconfiguration-memory");
> + if (!node)
> + return;
> +
> + prop = of_get_property(node, "ibm,dynamic-memory", NULL);
> + if (prop) {
> + __walk_drmem_v1_lmbs(prop, NULL, NULL, update_lmb);
> + } else {
> + prop = of_get_property(node, "ibm,dynamic-memory-v2", NULL);
> + if (prop)
> + __walk_drmem_v2_lmbs(prop, NULL, NULL, update_lmb);
> + }
> +
> + of_node_put(node);
> +}
> #endif
>
> static int init_drmem_lmb_size(struct device_node *dn)
> diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
> index ea4d6a660e0d..c68eccc6e8df 100644
> --- a/arch/powerpc/platforms/pseries/mobility.c
> +++ b/arch/powerpc/platforms/pseries/mobility.c
> @@ -25,6 +25,7 @@
>
> #include <asm/machdep.h>
> #include <asm/rtas.h>
> +#include <asm/drmem.h>
> #include "pseries.h"
> #include "../../kernel/cacheinfo.h"
>
> @@ -237,6 +238,7 @@ int pseries_devicetree_update(s32 scope)
> __be32 *data;
> int update_nodes_token;
> int rc;
> + bool drmem_updated = false;
>
> update_nodes_token = rtas_token("ibm,update-nodes");
> if (update_nodes_token == RTAS_UNKNOWN_SERVICE)
> @@ -271,6 +273,10 @@ int pseries_devicetree_update(s32 scope)
> continue;
> }
>
> + if (!strcmp(np->full_name,
> + "ibm,dynamic-reconfiguration-memory"))
> + drmem_updated = true;

Is there a reason that we can't use the existing pseries_memory_notifier()
callback in pseries/hotplug-memory.c to trigger the drmem_update_lmbs() when
either the ibm,dynamic-memory or ibm,dynamic-memory-v2 properties are updated?

Something like:

static int pseries_memory_notifier(struct notifier_block *nb,
unsigned long action, void *data)
{
struct of_reconfig_data *rd = data;
int err = 0;

switch (action) {
case OF_RECONFIG_ATTACH_NODE:
err = pseries_add_mem_node(rd->dn);
break;
case OF_RECONFIG_DETACH_NODE:
err = pseries_remove_mem_node(rd->dn);
break;
case OF_RECONFIG_UPDATE_PROPERTY:
if (!strcmp(rd->dn->full_name, "ibm,dynamic-reconfiguration-memory"));
drmem_update_lmbs(rd->prop);
break;
}
return notifier_from_errno(err);
}

Your drmem_update_lmbs() would need to be updated to take a property and to
check the property name against ibm,dyanmic-memory[-v2].

-Tyrel

> +
> switch (action) {
> case DELETE_DT_NODE:
> delete_dt_node(np);
> @@ -293,6 +299,9 @@ int pseries_devicetree_update(s32 scope)
> } while (rc == 1);
>
> kfree(rtas_buf);
> +
> + if (drmem_updated)
> + drmem_update_lmbs();
> return rc;
> }
>

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