Re: [PATCH] powerpc/pseries: Track LMB nid instead of using device tree

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

On 09/19/2018 11:38 PM, Michael Ellerman wrote:
> Nathan Fontenot <nfont@linux.vnet.ibm.com> writes:
> 
>> When removing memory we need to remove the memory from the node
>> it was added to instead of looking up the node it should be in
>> in the device tree.
>>
>> During testing we have seen scenarios where the affinity for a
>> LMB changes due to a partition migration or PRRN event. In these
>> cases the node the LMB exists in may not match the node the device
>> tree indicates it belongs in. This can lead to a system crash
>> when trying to DLAPR remove the LMB after a migration or PRRN
>> event. The current code looks up the node in the device tree to
>> remove the LMB from, the crash occurs when we try to offline this
>> node and it does not have any data, i.e. node_data[nid] == NULL.
> 
> This isn't building for 32-bit etc:
> 
> arch/powerpc/mm/drmem.c: In function 'init_drmem_v1_lmbs':
> arch/powerpc/mm/drmem.c:371:14: error: implicit declaration of function 'memory_add_physaddr_to_nid' [-Werror=implicit-function-declaration]
>    lmb->nid = memory_add_physaddr_to_nid(lmb->base_addr);
>               ^
> cc1: all warnings being treated as errors
> scripts/Makefile.build:317: recipe for target 'arch/powerpc/mm/drmem.o' failed
> 
> See the failed checks here:
>   https://patchwork.ozlabs.org/patch/969150/
> 
> 
> Probably drmem.c should only be compiled for 64-bit NUMA etc.

Looks like the root cause is that memory hotplug relies on sparsemem which
is not supported on 32-bit.

This patch is also going to need a refresh to apply cleanly due to other
patches that have gone in. I'll re-submit after looking at the build break issues more.

-Nathan

> 
> cheers
>