Greeting's 

Kernel Oops on my powerpc system when unloading driver mpt3sas.

Thanks Oliver for bisecting it to commit 3acac06 ("dma-mapping: merge
the generic remapping helpers into dma-direct")

Christoph, could you please have a look

Kernel version : latest mainline and next kernel
System : powerpc bare-metal
config: attached kernel config
test: rmmod mpt3sas

trace:
kernel: mpt3sas_cm0: enclosure logical id(0x500304801f080d3f), slot(12)
kernel: mpt3sas_cm0: enclosure level(0x0000), connector name(     )
kernel: mpt3sas_cm0: expander_remove: handle(0x0009),
sas_addr(0x500304801f080d3f)
kernel: mpt3sas_cm0: sending diag reset !!
kernel: mpt3sas_cm0: diag reset: SUCCESS
kernel: BUG: Unable to handle kernel data access on write at
0xc04a000000017c34
kernel: Faulting instruction address: 0xc0000000002f9c70
kernel: Oops: Kernel access of bad area, sig: 11 [#1]
kernel: LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA PowerNV
kernel: Dumping ftrace buffer:
kernel:   (ftrace buffer empty)
kernel: Modules linked in: ixgbe i40e iptable_mangle xt_MASQUERADE
iptable_nat nf_nat xt_conntrack nf_conntrack nf_defrag_ipv4 ipt_REJECT
nf_reject_ipv4 xt_tcpudp tun bridge stp llc iptable_filter btrfs
blake2b_generic xor zstd_decompress zstd_compress lzo_compress
vmx_crypto gf128mul raid6_pq powernv_rng rng_core kvm_hv kvm nfsd
binfmt_misc ip_tables x_tables autofs4 xfs libcrc32c qla2xxx nvme_fc
nvme_fabrics mdio nvme_core mpt3sas(-) raid_class scsi_transport_sas
[last unloaded: ixgbe]
kernel: CPU: 61 PID: 138496 Comm: rmmod Not tainted 5.5.0-rc3-autotest-autotest #1
kernel: NIP:  c0000000002f9c70 LR: c0000000001a9b44 CTR: c000000000049ef0
kernel: REGS: c000003f225af5e0 TRAP: 0380   Not tainted  (5.5.0-rc3-autotest-autotest)
kernel: MSR:  9000000000009033 <SF,HV,EE,ME,IR,DR,RI,LE>  CR: 24002424  XER: 20000000
kernel: CFAR: c0000000001a9b40 IRQMASK: 0 #012GPR00: c000000000049f88
c000003f225af870 c0000000012fc900 c04a000000017c00 #012GPR04:
0000000000000000 c000003fbbe70000 003e000000017c00 0000000000000000
#012GPR08: 0000000000000000 c0000000013ad000 c04a000000017c34
c00800000fbbe9e0 #012GPR12: c000000000049ef0 c000003ffffcaa80
0000000000000000 0000000000000000 #012GPR16: 0000000000000000
0000000000000000 0000010029f601e0 0000000010020098 #012GPR20:
0000000010020050 0000000010020038 0000000010020078 00000000100200b0
#012GPR24: 0000000000000000 c000000000d4c2f8 0000000005f00000
0000000000000000 #012GPR28: c00000000126e038 c000003fbbe70000
0000000000010000 c000003fdd22d0a8 
kernel: NIP [c0000000002f9c70] __free_pages+0x10/0x50
kernel: LR [c0000000001a9b44] dma_direct_free_pages+0x54/0x90
kernel: Call Trace:
kernel: [c000003f225af870] [c0000000001a9b44] dma_direct_free_pages+0x54/0x90 (unreliable)
kernel: [c000003f225af890] [c000000000049f88] dma_iommu_free_coherent+0x98/0xd0
kernel: [c000003f225af8e0] [c0000000001a8b78] dma_free_attrs+0xf8/0x100
kernel: [c000003f225af930] [c000000000310af4] dma_pool_destroy+0x174/0x200
kernel: [c000003f225af9d0] [c00800000fb917b8] _base_release_memory_pools+0x1d8/0x620 [mpt3sas]
kernel: [c000003f225afa60] [c00800000fb9b3b0] mpt3sas_base_detach+0x40/0x150 [mpt3sas]
kernel: [c000003f225afad0] [c00800000fbabdfc] _scsih_flush_running_cmds+0x5bc/0x1140 [mpt3sas]
kernel: [c000003f225afb90] [c00000000060eda4] pci_device_remove+0x64/0x110
kernel: [c000003f225afbd0] [c0000000006c4c44] device_release_driver_internal+0x154/0x260
kernel: [c000003f225afc10] [c0000000006c4e1c] driver_detach+0x8c/0x140
kernel: [c000003f225afc50] [c0000000006c2f28] bus_remove_driver+0x78/0x100
kernel: [c000003f225afc80] [c0000000006c5b30] driver_unregister+0x40/0x90
kernel: [c000003f225afcf0] [c00000000060e4c8] pci_unregister_driver+0x38/0x110
kernel: [c000003f225afd40] [c00800000fbbe338] cleanup_module+0x50/0x3fd8 [mpt3sas]
kernel: [c000003f225afda0] [c0000000001d866c] sys_delete_module+0x1dc/0x2a0
kernel: [c000003f225afe20] [c00000000000b9d0] system_call+0x5c/0x68
kernel: Instruction dump:
kernel: 88830051 2fa40000 41de0008 4bffe86c 7d234b78 4bfffe94 60000000 60420000
kernel: 3c4c0100 38422ca0 39430034 7c0004ac <7d005028> 3108ffff 7d00512d 40c2fff4
kernel: ---[ end trace ef72317ef11520bc ]---
kernel:
kernel: qla2xxx [0020:04:00.1]-b079:20: Removing driver
kernel: qla2xxx [0020:04:00.1]-00af:20: Performing ISP error recovery - ha=00000000ec46524c.
kernel: qla2xxx [0020:04:00.0]-b079:19: Removing driver
kernel: qla2xxx [0020:04:00.0]-00af:19: Performing ISP error recovery - ha=00000000af37b975.
kernel: qla2xxx [0020:03:00.1]-b079:18: Removing driver

-- 
Regard's

Abdul Haleem
IBM Linux Technology Centre