Re: [PATCH v3 01/11] xen/manage: keep track of the on-going suspend mode

[boris.ostrovsky@xxxxxxxxxx]

>>>>>>> Also, wrt KASLR stuff, that issue is still seen sometimes but I haven't 
>>>>>>> had
>>>>>>> bandwidth to dive deep into the issue and fix it.
>>>> So what's the plan there? You first mentioned this issue early this year 
>>>> and judged by your response it is not clear whether you will ever spend 
>>>> time looking at it.
>>>>
>>> I do want to fix it and did do some debugging earlier this year just haven't
>>> gotten back to it. Also, wanted to understand if the issue is a blocker to 
>>> this
>>> series?
>>
>> Integrating code with known bugs is less than ideal.
>>
> So for this series to be accepted, KASLR needs to be fixed along with other
> comments of course? 


Yes, please.



>>> I had some theories when debugging around this like if the random base 
>>> address picked by kaslr for the
>>> resuming kernel mismatches the suspended kernel and just jogging my memory, 
>>> I didn't find that as the case.
>>> Another hunch was if physical address of registered vcpu info at boot is 
>>> different from what suspended kernel
>>> has and that can cause CPU's to get stuck when coming online.
>>
>> I'd think if this were the case you'd have 100% failure rate. And we are 
>> also re-registering vcpu info on xen restore and I am not aware of any 
>> failures due to KASLR.
>>
> What I meant there wrt VCPU info was that VCPU info is not unregistered 
> during hibernation,
> so Xen still remembers the old physical addresses for the VCPU information, 
> created by the
> booting kernel. But since the hibernation kernel may have different physical
> addresses for VCPU info and if mismatch happens, it may cause issues with 
> resume. 
> During hibernation, the VCPU info register hypercall is not invoked again.


I still don't think that's the cause but it's certainly worth having a look.


-boris