I get this with the attached config (CONFIG_DEBUG_HIGHMEM)
INIT: version 2.85 booting
------------[ cut here ]------------
kernel BUG at arch/i386/mm/highmem.c:63!
invalid operand: 0000 [#1]
PREEMPT SMP DEBUG_PAGEALLOC
Modules linked in:
CPU: 0
EIP: 0060:[<c011d3a0>] Not tainted VLI
EFLAGS: 00010206 (2.6.10-rc1-mm4)
EIP is at kunmap_atomic+0x40/0xa0
eax: fffe3000 ebx: 00000011 ecx: 00000011 edx: 0001c000
esi: fffe4000 edi: fffe4000 ebp: c1e81dc8 esp: c1e81dc0
ds: 007b es: 007b ss: 0068
Process init (pid: 1, threadinfo=c1e80000 task=c1e50ae0)
Stack: 0000000f fffe6000 c1e81df4 c0156041 fffe4000 00000011 f6cc2dc0 00000000
f6cc2db4 00100173 c0000000 f6cc4bfc f6aa7bfc c1e81e28 c0156210 f6aa6d70
f6cc2d70 f6aa7bfc f6cc4bfc f6a9f0d0 c0000000 c0000000 00000000 c0000000
Call Trace:
[<c01080af>] show_stack+0x7f/0xa0
[<c0108263>] show_registers+0x163/0x1d0
[<c010849d>] die+0x10d/0x1a0
[<c01089d6>] do_invalid_op+0x106/0x110
[<c0107d2b>] error_code+0x2b/0x30
[<c0156041>] copy_pte_range+0xc1/0x1d0
[<c0156210>] copy_pmd_range+0xc0/0xd0
[<c015628c>] copy_pgd_range+0x6c/0x90
[<c01562f7>] copy_page_range+0x47/0x60
[<c0122c62>] copy_mm+0x2d2/0x3c0
[<c0123786>] copy_process+0x506/0xe60
[<c01241e1>] do_fork+0x71/0x1d2
[<c0105c29>] sys_clone+0x39/0x40
[<c01071c5>] sysenter_past_esp+0x52/0x71
Code: 55 23 00 81 e6 00 f0 ff ff 8d 04 40 8d 04 c0 81 fe ff 8f fb ff 8d 0c
18 76 30 8d 51 0b b8 00 f0 ff ff c1 e2 0c 29 d0 39 c6 74 08 <0f> 0b 3f 00
32 52 61 c0 a1 c0 fd 7a c0 8d 14 8d 00 00 00 00 29