Re: [Qemu-devel] Re: [PATCH] x86: Reboot CPU on triple fault - Version 4

[Anthony Liguori <anthony@codemonkey.ws>]

Jan Kiszka wrote:
> Anthony Liguori wrote:
>   
>> Jan Kiszka wrote:
>>     
>> You can always check within the guest to see if it's rebooted (via
>> uptime for instance).
>>     
>
> But you won't find the CPU state on triple fault there.
>   

Nor will you with your patch.

>> It's extremely unlikely you'll ever see an OS triple fault in the wild
>> unless you're doing kernel development.  Triple faulting requires a bad
>> IDT or a really bad page table both of which are not something an OS is
>> likely to do by accident.  If your OS is triple faulting, I highly doubt
>> it's just going to reboot and everything's going to be okay.
>>     
>
> There are various OSes out there in the wild. Not all of them conform to
> common assumptions about how OSes typically look like. And once you
> start moving things under a different roof (like QEMU), you are better
> off logging such /potentially/ critical events (specifically if that
> roof is a bit smaller due to missing segment limit and type checks).
> That's at least our situation ATM.
>   

It's not a question of whether it's logged, it's a question of whether 
it gets logged *specially*.  That's the crux of the discussion here.  My 
argument is that triple faults are not sufficiently special that they 
warrant *special* logging.

Regards,

Anthony Liguori