right now i'm trying to bisect this crash on 64-bit:

 Calling initcall 0xffffffff80395877: pci_init+0x0/0x2b()
 ------------[ cut here ]------------
 kernel BUG at arch/x86/mm/pageattr_64.c:176!
 [...]
 Call Trace:
  [<ffffffff8021db68>] change_page_attr_addr+0x9e/0x119
  [<ffffffff8021d44f>] ioremap_change_attr+0x49/0x58
  [<ffffffff8021d626>] iounmap+0xbe/0xe0
  [<ffffffff804dfc95>] quirk_usb_early_handoff+0x396/0x3a5
  [<ffffffff80396ea0>] pci_fixup_device+0x90/0x9e
  [<ffffffff80395889>] pci_init+0x12/0x2b
  [<ffffffff808c9545>] kernel_init+0xd0/0x23c
  [<ffffffff8020bec8>] child_rip+0xa/0x12
  [<ffffffff808c9475>] kernel_init+0x0/0x23c
  [<ffffffff8020bebe>] child_rip+0x0/0x12

config and bootlog attached.

it's one of these patches:

 Subject: x86: move all asm/pgtable constants into one place
 Subject: x86: avoid name conflict for Voyager leave_mm
 Subject: x86/pgtable: unify pagetable accessors

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