linux-kernel - Re: ce56a86e2a ("x86/mm: Limit mmap() of /dev/mem to valid physical addresses"): kernel BUG at arch/x86/mm/physaddr.c:79!

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Message-ID: <8721eeac-a644-e815-55e9-5f01956dd22a@eikelenboom.it>
Date:   Thu, 26 Oct 2017 10:58:16 +0200
From:   Sander Eikelenboom <linux@...elenboom.it>
To:     Craig Bergstrom <craigb@...gle.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:     Fengguang Wu <fengguang.wu@...el.com>, wfg@...ux.intel.com,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        LKP <lkp@...org>
Subject: Re: ce56a86e2a ("x86/mm: Limit mmap() of /dev/mem to valid physical
 addresses"): kernel BUG at arch/x86/mm/physaddr.c:79!

On 26/10/17 10:12, Sander Eikelenboom wrote:
> On 26/10/17 10:05, Sander Eikelenboom wrote:
>> On 26/10/17 00:02, Craig Bergstrom wrote:
>>> Thanks for the notification, my apologies for the breakage.  I'll take a
>>> close look and see if I can figure out what went wrong.
>>>
>>> Sander, any chance you can send /proc/iomem and the inputs to the mmap call
>>> that fail on your affected system?
>>
>> Hi Craig,
>>
>> The output from /proc/iomem is simple to get and attached.
>> The mmap call is probably issued by qemu and will require more digging.
> 
> Ahh grepping qemu gave a pointer, it's probably the code in:
> 
> http://xenbits.xen.org/gitweb/?p=qemu-xen.git;a=blob;f=hw/xen/xen_pt_msi.c;h=ff9a79f5d27ad7d74a1b22297be560feb455063c;hb=5cd7ce5dde3f228b3b669ed9ca432f588947bd40
> 
> around line 571, that would also explain why it's only this device that
> has the problem, since it's the only one trying to use MSI(-X)
> interrupts. Will see it i can add some logging to that function.

Attached is the qemu debug output with an extra line outputting all stuff
used to calculate the arguments used by the mmap-call.
--
Sander

 
> --
> Sander
> 
> 
>>
>> I don't know if there is that much time left for 4.14, since we are at
>> RC6 already.
>>
>> --
>> Sander
>>
>>
>>>
>>>
>>> On Wed, Oct 25, 2017 at 2:50 PM, Boris Ostrovsky <boris.ostrovsky@...cle.com
>>>> wrote:
>>>
>>>> On 10/23/2017 10:44 PM, Fengguang Wu wrote:
>>>>> Greetings,
>>>>>
>>>>> 0day kernel testing robot got the below dmesg and the first bad commit is
>>>>>
>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>>>> master
>>>>>
>>>>> commit ce56a86e2ade45d052b3228cdfebe913a1ae7381
>>>>> Author:     Craig Bergstrom <craigb@...gle.com>
>>>>> AuthorDate: Thu Oct 19 13:28:56 2017 -0600
>>>>> Commit:     Ingo Molnar <mingo@...nel.org>
>>>>> CommitDate: Fri Oct 20 09:48:00 2017 +0200
>>>>>
>>>>>      x86/mm: Limit mmap() of /dev/mem to valid physical addresses
>>>>
>>>> Also note
>>>> https://lists.xenproject.org/archives/html/xen-devel/2017-10/msg02935.html
>>>>
>>>> -boris
>>>>
>>>
>>
> 


View attachment "qemu-dm-guest.log" of type "text/x-log" (27730 bytes)