[Xen-devel] bad type error in get_page_type() line 1525

["King, Steven R" <steven.r.king@xxxxxxxxx>]

Hello all,

I'm getting the "Bad type" error in get_page_type() around line 1525.
The situation is this:

Linux domU driver creates a user-mode mapping to a shared-page,
including calling create_lookup_pte_addr() which returns a ptep of
0xA69B0EDC.

App in domU user-mode accesses the page without problem.

When the app exits, the driver cleans up, then the OS cleans up the
memory space previously owned by the process.  In the course of doing
this, the kernel hits a BUG():

kernel BUG at arch/i386/mm/pgtable-xen.c:511!
invalid operand: 0000 [#1]
SMP
Modules linked in:
CPU:    0
EIP:    0061:[<c0113520>]    Not tainted VLI
EFLAGS: 00010282   (2.6.14-xenU)
EIP is at pgd_walk+0x160/0x170
eax: ffffffea   ebx: cf25f000   ecx: a69b0063   edx: 00000000
esi: 00000000   edi: cf20eb7c   ebp: cf23be90   esp: cf23be70
ds: 007b   es: 007b   ss: 0069
Process gan_microbench (pid: 482, threadinfo=cf23a000 task=cf9d8530)
Stack: 00000000 00000000 000002df cf20eb7c cf20eb7c 001e41c0 cf20e000
cf4f4800
       cf23bea8 c01135b4 cf20e000 00000063 cf4f4800 cf4f4840 cf23bebc
c0113674
       cf20e000 cf23becc c1000000 cf23bef8 c011374e cf4f4800 cf9d89dc
00000005
Call Trace:
 [<c010845f>] show_stack+0x7f/0xa0
 [<c0108612>] show_registers+0x162/0x1d0
 [<c0108824>] die+0xf4/0x180
 [<c02adb85>] do_trap+0xb5/0xc0
 [<c0108bec>] do_invalid_op+0xbc/0xd0
 [<c0108127>] error_code+0x2b/0x30
 [<c01135b4>] __pgd_unpin+0x34/0x50
 [<c0113674>] mm_unpin+0x24/0x40
 [<c011374e>] _arch_exit_mmap+0x6e/0x180
 [<c0152db2>] exit_mmap+0x22/0x1a0
 [<c011a8e6>] mmput+0x36/0x90
 [<c011eeb5>] exit_mm+0xe5/0x100
 [<c011f864>] do_exit+0xd4/0x3e0
 [<c011fbec>] do_group_exit+0x3c/0xb0
 [<c011fc75>] sys_exit_group+0x15/0x20
 [<c0107f81>] syscall_call+0x7/0xb
Code: 7f c1 e1 0c 09 d9 be 01 00 00 00 31 d2 8b 5d 08 e8 b6 0c ff ff 85
c0 75 08 83 c4 14 5b 5e 5f 5d c3 0f 0b 22 02 b0 6f 2c c0 eb ee <0f> 0b
ff 01 b0 6f 2c c0 e9 63 ff ff ff 8d 76 00 55 89 e5 83 ec
 <1>Fixing recursive fault but reboot is needed!
Xen reports:

(XEN) DOM1: (file=mm.c, line=1531) Bad type (saw 32df0004 != exp
e0000000) for m
fn a69b0 (pfn f25f)
(XEN) DOM1: (file=mm.c, line=478) Error getting mfn a69b0 (pfn f25f)
from L1 ent
ry a69b0063 for dom1

I notice that the offending mfn correlates to the ptep I got back from
create_lookup_pte_addr().

I anybody can offer a clue as to what is going wrong, I'd much
appreciate it!

Thanks,
-steve

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