Re: [Xen-devel] Is: EPT violations. Was:Re: Problems with pci/vga passthrough

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 01/24/2017 01:51 PM, Boris Ostrovsky wrote:
> On 01/24/2017 01:44 PM, Diederik de Haas wrote:
>> On dinsdag 24 januari 2017 13:28:28 CET Boris Ostrovsky wrote:
>>>>> Reported it at https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=852324
>>>>> but  given Ben Hutchings' reaction it seems to be a Xen problem after
>>>>> all.
>>>>>
>>>>> Relevant part of earlier attached dmesg:
>>>>>
>>>>> [   13.588386] WARNING: CPU: 18 PID: 1 at 
>>>>> /build/linux-zDY19G/linux-4.8.15/arch/x86/mm/dump_pagetables.c:225
>>>>> note_page+0x5e8/0x790 [   13.588388] x86/mm: Found insecure W+X mapping
>>>>> at address ffff880000000000/0xffff880000000000 ...
>>>>> [   13.608867] x86/mm: Checked W+X mappings: FAILED, 4602 W+X pages
>>>>> found.
>>>> Now this is a know issue, but I'm pretty convinced one that's entirely
>>>> unrelated to your problem.
>>> I thought we fixed this. That's what is_hypervisor_range() was
>>> introduced for, and I haven't seen this warning since then.


Actually, I do see the warnings (I usually don't set CONFIG_DEBUG_WX).
They are not for the hypervisor range though, so the commit below is not
relevant.

Nevertheless, as Jan said, it's unlikely to cause your problem.

-boris


>> When? Which commit?
>> Maybe it isn't (yet) in the Debian tree and/or I am using a kernel which 
>> doesn't contain that fix.
>
> Commit f4e342c87776884f0309942a3880ca7e835239f9.
>
> All it did was to prevent the walker from trying to verify pages in the
> hypervisor range so it doesn't really fix anything. It's just that I am
> surprised to see this warning again.

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