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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Date:   Thu, 26 Oct 2017 10:12:15 +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 10:05, 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.

--
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
>>>
>>
>