[6.1.0-rc3-next-20221104] Boot failure - kernel BUG at mm/memblock.c:519

[Sachin Sant]

While booting recent linux-next on a IBM Power10 Server LPAR
following crash is observed:

[    0.000000] numa: Partition configured for 32 NUMA nodes.
[    0.000000] ------------[ cut here ]------------
[    0.000000] kernel BUG at mm/memblock.c:519!
[    0.000000] Oops: Exception in kernel mode, sig: 5 [#1]
[    0.000000] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
[    0.000000] Modules linked in:
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 6.1.0-rc3-next-20221104 #1
[    0.000000] Hardware name: IBM,9080-HEX POWER10 (raw) 0x800200 0xf000006 of:IBM,FW1030.00 (NH1030_026) hv:phyp pSeries
[    0.000000] NIP:  c0000000004ba240 LR: c0000000004bb240 CTR: c0000000004ba210
[    0.000000] REGS: c000000002a8b7b0 TRAP: 0700   Not tainted  (6.1.0-rc3-next-20221104)
[    0.000000] MSR:  8000000000021033 <SF,ME,IR,DR,RI,LE>  CR: 24042424  XER: 00000001
[    0.000000] CFAR: c0000000004ba290 IRQMASK: 1 
[    0.000000] GPR00: c0000000004bb240 c000000002a8ba50 c00000000136ee00 c0000010f3ac00a8 
[    0.000000] GPR04: 0000000000000000 c0000010f3ac0090 00000010f3ac0000 0000000000000d00 
[    0.000000] GPR08: 0000000000000001 0000000000000007 0000000000000001 0000000000000081 
[    0.000000] GPR12: c0000000004ba210 c000000002e10000 0000000000000000 000000000000000d 
[    0.000000] GPR16: 000000000f6be620 000000000f6be8e8 000000000f6be788 000000000f6bed58 
[    0.000000] GPR20: 000000000f6f6d58 c0000000029a8de8 00000010f3ad8800 0000000000000080 
[    0.000000] GPR24: 00000010f3ad7b00 0000000000000000 0000000000000100 0000000000000d00 
[    0.000000] GPR28: 00000010f3ad7b00 c0000000029a8de8 c0000000029a8e00 0000000000000006 
[    0.000000] NIP [c0000000004ba240] memblock_merge_regions.isra.12+0x40/0x130
[    0.000000] LR [c0000000004bb240] memblock_add_range+0x190/0x300
[    0.000000] Call Trace:
[    0.000000] [c000000002a8ba50] [0000000000000100] 0x100 (unreliable)
[    0.000000] [c000000002a8ba90] [c0000000004bb240] memblock_add_range+0x190/0x300
[    0.000000] [c000000002a8bb10] [c0000000004bb5e0] memblock_reserve+0x70/0xd0
[    0.000000] [c000000002a8bba0] [c000000002045234] memblock_alloc_range_nid+0x11c/0x1e8
[    0.000000] [c000000002a8bc60] [c0000000020453a4] memblock_alloc_internal+0xa4/0x110
[    0.000000] [c000000002a8bcb0] [c0000000020456cc] memblock_alloc_try_nid+0x94/0xcc
[    0.000000] [c000000002a8bd40] [c00000000200b570] alloc_paca_data+0x7c/0xcc
[    0.000000] [c000000002a8bdb0] [c00000000200b770] allocate_paca+0x8c/0x28c
[    0.000000] [c000000002a8be50] [c00000000200a26c] setup_arch+0x1c4/0x4d8
[    0.000000] [c000000002a8bed0] [c000000002004378] start_kernel+0xb4/0xa84
[    0.000000] [c000000002a8bf90] [c00000000000da90] start_here_common+0x1c/0x20
[    0.000000] Instruction dump:
[    0.000000] 7c0802a6 fba1ffe8 fbc1fff0 fbe1fff8 7c7d1b78 7c9e2378 3be00000 f8010010 
[    0.000000] f821ffc1 e9230000 3969ffff 4800000c <0b0a0000> 7d3f4b78 393f0001 7fbf5840 
[    0.000000] ---[ end trace 0000000000000000 ]---
[    0.000000] 
[    0.000000] Kernel panic - not syncing: Fatal exception
[    0.000000] Rebooting in 180 seconds..

This problem was introduced with next-20221101. Git bisect points to
following patch

commit 3f82c9c4ac377082e1230f5299e0ccce07b15e12
Date:   Tue Oct 25 15:09:43 2022 +0800
    memblock: don't run loop in memblock_add_range() twice

Reverting this patch helps boot the kernel to login prompt.

Have attached .config

- Sachin

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