Subject: linux-next: boot failure after merge of the iomem-mmap-vs-gup tree

From: Stephen Rothwell <[email-masked]>
Date: Wed, 13 Jan 2021 16:29:48 +1100

Hi all,

After merging the iomem-mmap-vs-gup tree, today's linux-next boot test
(powerpc pseries_le_defconfig) failed like this:

    EEH: pSeries platform initialized
    PCI: Probing PCI hardware
    BUG: Kernel NULL pointer dereference on write at 0x00000030
    Faulting instruction address: 0xc00000000013bf4c
    Oops: Kernel access of bad area, sig: 11 [#1]
    LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
    Modules linked in:
    CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.11.0-rc3 #2
    NIP:  c00000000013bf4c LR: c0000000007a9ee8 CTR: 0000000000000000
    REGS: c0000000063a3610 TRAP: 0380   Not tainted  (5.11.0-rc3)
    MSR:  8000000002009033 <SF,VEC,EE,ME,IR,DR,RI,LE>  CR: 84002440  XER: 00000000
    CFAR: c0000000007a9ee4 IRQMASK: 0 
    GPR00: c0000000007a9ee8 c0000000063a38b0 c0000000013d8100 c000000006061300 
    GPR04: 0000000000000000 0000000000000b20 c000000000f11738 000000000000ffff 
    GPR08: c0000000007a7ab0 0000000000000000 c0000000007a7a40 2d6770696f730000 
    GPR12: 0000000000000000 c0000000015b0000 c000000000013120 0000000000000000 
    GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 
    GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 
    GPR24: c000000006210de8 c000000006167120 c000000006620b20 0000000000000000 
    GPR28: c000000006167120 0000000000000180 c000000006061300 c000000006167000 
    NIP [c00000000013bf4c] iomem_get_mapping+0x1c/0x30
    LR [c0000000007a9ee8] pci_create_legacy_files+0xa8/0x1c0
    Call Trace:
    [c0000000063a38b0] [c0000000007a9e84] pci_create_legacy_files+0x44/0x1c0 (unreliable)
    [c0000000063a3930] [c000000000795198] pci_register_host_bridge+0x288/0x510
    [c0000000063a3a60] [c000000000795514] pci_create_root_bus+0xf4/0x150
    [c0000000063a3ac0] [c00000000006d424] pcibios_scan_phb+0xe4/0x270
    [c0000000063a3b70] [c000000001010b40] pcibios_init+0x8c/0x128
    [c0000000063a3bf0] [c000000000012b70] do_one_initcall+0x60/0x2c0
    [c0000000063a3cc0] [c0000000010046b4] kernel_init_freeable+0x2e8/0x380
    [c0000000063a3da0] [c000000000013144] kernel_init+0x2c/0x168
    [c0000000063a3e10] [c00000000000dff0] ret_from_kernel_thread+0x5c/0x6c
    Instruction dump:
    7c634850 4e800020 60000000 60000000 60420000 3c4c012a 3842c1d0 7c0802a6 
    60000000 3d22000d e929caf8 7c2004ac <e8690030> 4e800020 60000000 60000000 
    ---[ end trace 77f55ece72f02708 ]---
    
    Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b

Caused by commit

  85482fbab59e ("PCI: Revoke mappings like devmem")

Reverting that commit fixes the boot, so I have done that for today.

-- 
Cheers,
Stephen Rothwell