Re: [PATCH] KVM: SVM: fix random segfaults with NPT enabled

[Avi Kivity <avi@qumranet.com>]

Joerg Rodel wrote:

 

>> hm.  tbench doesn't allocate memory, so there shouldn't be any npt faults.  I don't 
>> see how this can make a difference.
>>     
>
>   

I reproduced it.  There are a few npt faults as the guest has not 
touched all of memory yet.  If I force it to touch all of memory (dd < 
/dev/hda), the problem appears to go away.

> Base for the fix was this bugreport:
>
> http://sourceforge.net/tracker/index.php?func=detail&aid=2019053&group_id=180599&atid=893831
>
> We found out that the same crash occur on long running compile
> workloads and that stale tlb-entries cause it. Until we find the real
> location of the missing tlb flush in the mmu code, i think its best to
> flush the TLB every time the mapping/unmapping code for the nested page
> table is executed. This fixes at least the crashes in the guest and has
> only minimal performance impact.
>   

I'd like to try and find out what the problem is exactly.  Otherwise we 
may be only narrowing the window, not closing it.

-- 
error compiling committee.c: too many arguments to function