[PATCH v2] powerpc/pseries: Track LMB nid instead of using device tree

[Michael Ellerman]

On Tue, 2018-10-02 at 15:35:59 UTC, Nathan Fontenot wrote:
> 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 DLPAR 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.
> 
> 36:mon> e
> cpu 0x36: Vector: 300 (Data Access) at [c0000001828b7810]
>     pc: c00000000036d08c: try_offline_node+0x2c/0x1b0
>     lr: c0000000003a14ec: remove_memory+0xbc/0x110
>     sp: c0000001828b7a90
>    msr: 800000000280b033
>    dar: 9a28
>  dsisr: 40000000
>   current = 0xc0000006329c4c80
>   paca    = 0xc000000007a55200   softe: 0        irq_happened: 0x01
>     pid   = 76926, comm = kworker/u320:3
> 
> 36:mon> t
> [link register   ] c0000000003a14ec remove_memory+0xbc/0x110
> [c0000001828b7a90] c00000000006a1cc arch_remove_memory+0x9c/0xd0 (unreliable)
> [c0000001828b7ad0] c0000000003a14e0 remove_memory+0xb0/0x110
> [c0000001828b7b20] c0000000000c7db4 dlpar_remove_lmb+0x94/0x160
> [c0000001828b7b60] c0000000000c8ef8 dlpar_memory+0x7e8/0xd10
> [c0000001828b7bf0] c0000000000bf828 handle_dlpar_errorlog+0xf8/0x160
> [c0000001828b7c60] c0000000000bf8cc pseries_hp_work_fn+0x3c/0xa0
> [c0000001828b7c90] c000000000128cd8 process_one_work+0x298/0x5a0
> [c0000001828b7d20] c000000000129068 worker_thread+0x88/0x620
> [c0000001828b7dc0] c00000000013223c kthread+0x1ac/0x1c0
> [c0000001828b7e30] c00000000000b45c ret_from_kernel_thread+0x5c/0x80
> 
> To resolve this we need to track the node a LMB belongs to when
> it is added to the system so we can remove it from that node instead
> of the node that the device tree indicates it should belong to.
> 
> Signed-off-by: Nathan Fontenot <nfont at linux.vnet.ibm.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/b2d3b5ee66f2a04a918cc043cec0c9ed

cheers