fbx_5.15 WARN_ON() at boot with CONFIG_DEBUG_VM

[Maxime Bizon]

Hello,

With CONFIG_DEBUG_VM=y, early_iounmap() triggers this:

	VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep));

[    0.292811] WARNING: CPU: 0 PID: 1 at arch/powerpc/mm/pgtable.c:194 set_pte_at+0x8c/0x21c
[    0.301053] CPU: 0 PID: 1 Comm: swapper Tainted: G        W         5.15.0+ #402
[    0.308473] NIP:  8001d96c LR: 8001d960 CTR: 00000000
[    0.313520] REGS: 810fbc10 TRAP: 0700   Tainted: G        W          (5.15.0+)
[    0.320749] MSR:  00029032 <EE,ME,IR,DR,RI>  CR: 48008804  XER: 00000000
[    0.327705] 
[    0.327705] GPR00: 8001d960 810fbcc0 810c8020 80ce4004 8001d8e0 80ce4004 00000000 810fbcd0 
[    0.327705] GPR08: 00000007 00000001 00000000 80950ed4 28000804 00000000 8000673c 00000000 
[    0.327705] GPR16: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
[    0.327705] GPR24: 80d01ef8 80b8dca0 00000000 80d01000 ef801000 00000000 f021f79a 80ce4004 
[    0.363822] NIP [8001d96c] set_pte_at+0x8c/0x21c
[    0.368462] LR [8001d960] set_pte_at+0x80/0x21c
[    0.373009] Call Trace:
[    0.375443] [810fbcc0] [8001d960] set_pte_at+0x80/0x21c (unreliable)
[    0.381891] [810fbd30] [8001e8cc] map_kernel_page+0x120/0x1a4
[    0.387707] [810fbda0] [80179a18] __set_fixmap+0x38/0x4c
[    0.393096] [810fbdb0] [809a772c] early_iounmap+0x184/0x218
[    0.398733] [810fbdf0] [80995db0] ioremap_legacy_serial_console+0x108/0x150
[    0.405803] [810fbe20] [8099144c] do_one_initcall+0xe8/0x228
[    0.411541] [810fbed0] [809916ec] kernel_init_freeable+0xdc/0x378
[    0.417718] [810fbf20] [80006764] kernel_init+0x28/0x118
[    0.423107] [810fbf40] [80016148] ret_from_kernel_thread+0x14/0x1c
[    0.429380] Instruction dump:
[    0.432349] 913e0004 7cbf2b78 915e0000 38610030 90c10030 4815a605 7fe3fb78 83a10030 
[    0.440363] 4815a5f9 813f0000 71290001 41820010 <0fe00000> 9361005c 93810060 93810060 
[    0.448553] ---[ end trace 523b05d3a0288818 ]---

-- 
Maxime