Hi,

I am observing below traces, while running memory hotplug on Power-9 ZZ 
machine, on main line kernel.

Machine: Power9 ZZ
Kernel: Linux main line 4.18.0-rc2(commit head: 
813835028e9ae1f18cd11bb0ec591d0f0577d96a)
Test: 
https://github.com/avocado-framework-tests/avocado-misc-tests/blob/master/memory/memhotplug.py

Attached is .config file.

Traces:

[ 1941.624891] swapper/0: page allocation failure: order:0, mode:0x0(), 
nodemask=(null)
  [ 1941.624910] swapper/0 cpuset=/ mems_allowed=0-255
  [ 1941.624926] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G            E    
  4.18.0-rc2-autotest-autotest #1
  [ 1941.624933] Call Trace:
  [ 1941.624943] [c000000ffffcb4f0] [c00000000099966c] 
dump_stack+0xb0/0xf4 (unreliable)
  [ 1941.624954] [c000000ffffcb530] [c00000000028a6d8] 
warn_alloc+0xe8/0x180
  [ 1941.624964] [c000000ffffcb5e0] [c00000000028b058] 
__alloc_pages_nodemask+0x858/0xf80
  [ 1941.624974] [c000000ffffcb7b0] [c000000000044fb0] 
iommu_alloc_coherent+0x90/0x1b0
  [ 1941.624986] [c000000ffffcb850] [c000000000042fd8] 
dma_iommu_alloc_coherent+0x38/0x60
  [ 1941.624997] [c000000ffffcb870] [d00000000e4923d4] 
send_srp_login+0x854/0x910 [ibmvscsi]
  [ 1941.625007] [c000000ffffcb920] [c00000000067041c] 
scsi_dispatch_cmd+0xdc/0x2f0
  [ 1941.625017] [c000000ffffcb9a0] [c000000000672c54] 
scsi_request_fn+0x544/0x940
  [ 1941.625027] [c000000ffffcbab0] [c0000000004c8804] 
__blk_run_queue+0x64/0xa0
  [ 1941.625035] [c000000ffffcbae0] [c0000000004c88c4] 
blk_run_queue+0x44/0x80
  [ 1941.625043] [c000000ffffcbb10] [c00000000066f714] 
scsi_run_queue+0x2e4/0x3a0
  [ 1941.625053] [c000000ffffcbb80] [c000000000673560] 
scsi_end_request+0x1e0/0x270
  [ 1941.625062] [c000000ffffcbbe0] [c000000000673834] 
scsi_io_completion+0x244/0x730
  [ 1941.625072] [c000000ffffcbcb0] [c000000000668208] 
scsi_finish_command+0x148/0x1b0
  [ 1941.625082] [c000000ffffcbd30] [c0000000006726b8] 
scsi_softirq_done+0x198/0x1f0
  [ 1941.625091] [c000000ffffcbdc0] [c0000000004d8f20] 
blk_done_softirq+0xc0/0xf0
  [ 1941.625101] [c000000ffffcbe00] [c0000000009baf6c] 
__do_softirq+0x14c/0x3a4
  [ 1941.625111] [c000000ffffcbef0] [c0000000001087a8] 
irq_exit+0x1a8/0x1c0
  [ 1941.625120] [c000000ffffcbf20] [c0000000000167c8] 
__do_irq+0x98/0x200
  [ 1941.625129] [c000000ffffcbf90] [c000000000028424] 
call_do_irq+0x14/0x24
  [ 1941.625137] [c00000000114fa40] [c0000000000169c4] do_IRQ+0x94/0x110
  [ 1941.625145] [c00000000114fa90] [c000000000008c24] 
hardware_interrupt_common+0x114/0x120
  [ 1941.625157] --- interrupt: 501 at snooze_loop+0x98/0x1e0

Regards,
Venkat.