Re: [Qemu-devel] kvm: sync registers?

[Anthony Liguori]

Paul Brook wrote:
> On Friday 07 November 2008, Anthony Liguori wrote:
>   
> > Gerd Hoffmann wrote:
> >     
> > >   Hi,
> > >
> > > How does kvm sync registers between kernel and qemu env?
> > > I see there are kvm_arch_{get,put}_registers() functions in
> > > target-i386/kvm.c, but grep doesn't find a single call of them?
> > >       
> > Right now, it doesn't.  We should probably sync registers in the same
> > places that kvm-userspace does (gdbstubs, vmport, etc.).
> >
> > I tried to always sync registers on every exit but this causes boot to
> > fail. The same is true of kvm-userspace though and I've been meaning to
> > dig into why this is.
> >     
>
> Maybe due to do with inconsistencies between the segment register contents and 
> the descriptor tables? I know I've written code that relies on this feature.
>   

VT/SVM actually allow you to get at the descriptor tables/cache and we 
save/restore them in KVM.  I only see this issue if I always 
save/restore registers so it leads me to think it's something more subtle.

Regards,

Anthony Liguori

> Paul
>