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

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Date:	Thu, 21 Aug 2008 12:07:18 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Jeremy Fitzhardinge" <jeremy@...p.org>
Cc:	"Rafał Miłecki" <zajec5@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"Kernel Testers List" <kernel-testers@...r.kernel.org>,
	"Ingo Molnar" <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	"Jack Steiner" <steiner@....com>,
	"Alan Jenkins" <alan-jenkins@...fmail.co.uk>,
	"Hugh Dickens" <hugh@...itas.com>
Subject: Re: [Bug #11313] Plugging HDMI causes "unable to handle kernel paging request"

On Thu, Aug 21, 2008 at 11:13 AM, Jeremy Fitzhardinge <jeremy@...p.org> wrote:
> 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
>                                               ^^^^^^^^^^

this is just estimated. and worst case.

> 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]
>                                                     ^^^^^^^^^^^^^^^^^^^^^^^
this is correct value used finally.
>
> 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.
> <<<<

YH