Re: kernel bug in kvm_intel

[Avi Kivity]

On 11/01/2009 12:45 PM, Tejun Heo wrote:
> Hello,
>
> Avi Kivity wrote:
>    
> > We get a page fault immediately (next instruction) after returning from
> > the guest when running with oprofile.  The page fault address does not
> > match anything the instruction does, so presumably it is one of the
> > accesses the processor performs in order to service an NMI (ordinary
> > interrupts are masked; and the fact that it happens with oprofile
> > strengthens this assumption).
> >      
> Ah... okay, that's tricky but IIRC faults like that can be
> distinguished from regular ones via processor state, right?
>    

Not on x86.  But given that the fault address is different from %rsp 
(which is what the instruction accesses) and %rip, there aren't many 
alternatives.

> > Here is the code in question:
> >
> >      
> > >      3ae7:       75 05                   jne    3aee<vmx_vcpu_run+0x26a>
> > >        3ae9:       0f 01 c2                vmlaunch
> > >        3aec:       eb 03                   jmp    3af1<vmx_vcpu_run+0x26d>
> > >        3aee:       0f 01 c3                vmresume
> > >        3af1:       48 87 0c 24             xchg   %rcx,(%rsp)
> > >        
> > ^^^ fault, but not at (%rsp)
> >      
> Can you please post the full oops (including kernel debug messages
> during boot) or give me a pointer to the original message?

http://www.mail-archive.com/kvm@xxxxxxxxxxxxxxx/msg23458.html

> Also, does
> the faulting address coincide with any symbol?
>    

No (at least, not in System.map).

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

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