Re: [Bug #11313] Plugging HDMI causes "unable to handle kernel paging request"

Jeremy Fitzhardinge
2008-08-21T18:13:21Z

Rafał Miłecki wrote:
> I added full dmesg 5 minutes after adding grepped:
> http://bugzilla.kernel.org/attachment.cgi?id=17331
>

OK, I think I see the problem (pasted from bugzilla comment):

>>>>
Some notes as I pick through all the evidence so far:

- the crash is specifically because there are reserved bits set in the pmd
- the pmd is b02a00043a6001a3 in both cases
- the vaddr is ffff88013a600000 in the first crash, and
ffff81013a6d1c00 in the second
corresponding to the same large-page pmd mapping of phys page 0x13a600000
- this maps to e820 entry
BIOS-e820: 0000000100000000 - 0000000140000000 (usable)
- the corresponding boot-time mapping is

init_memory_mapping
0100000000 - 0140000000 page 2M
kernel direct mapping tables up to 140000000 @ b000-11000
^^^^^^^^^^
addr 100000000 reusing pgd 201880 0000000000202063
last_map_addr: 140000000 end: 140000000

!!! and the memory allocated for this pagetable is:
#5 [0000008000 - 000000b000] PGTABLE ==> [0000008000 - 000000b000]
#6 [000000b000 - 000000c000] PGTABLE ==> [000000b000 - 000000c000]
^^^^^^^^^^^^^^^^^^^^^^^

IOW, it's mapping using b000-11000, but it has only reserved b000 - c000

Also, this is right in the middle of the ISA area, which seems risky.
<<<<

Bug #11237 shows the same symptom, so I'm pretty confident they're dups now.

J