Re: [Xen-devel] xen,bproc and grub

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

Oh yes. It's only a problem for SMP guests anyway (which are making
excellent progress but not ready for check-in yet). Since we currently
just enclose any suspect code in Xen with a "big fat domain lock"
right now, we couldn't have any problem as only one "virtual cpu" can
update pagetables at any point in time. The PAT trick was looking
forward to the possibility that we could allow vcpus to go at their
pagetables with no locking in Xen required. That now won't be
possible, but I expect that isn't a problem. I just like lock-free
code, is all. :-)

 -- Keir

> Any other possible solutions?
> 
> 
>                               -Kip
> 
> 
> On Tue, 16 Nov 2004, Keir Fraser wrote:
> 
> >
> > Ah yes, if VMs use PSE then we were plannign to abuse PAT to provide
> > some protection for us. However, VMs can *not* currently use PSE at
> > the moment and, even if they could, we have since discovered that our
> > abuse of PAT would not work anyway. :-)
> >
> >  -- Keir
> >
> > >
> > > I was told there were security issues with allowing PSE in VMs outright.
> > >
> > >                           -Kip
> > >
> > > >
> > > > The two features are completely unrelated.
> > > >
> > > >  -- Keir
> > > >
> > > > > My understanding was that PAT would likely be used to allow VMs to use
> > > > > PSE, is that not correct?
> > > > >
> > > > >               -Kip
> > > > >
> > > > > > > We don't use SYSCALL/SYSENTER, PAT or VME.
> > > > > >
> > > > > > ah, good.
> > > > > >
> > > > > >
> > > > > >
> > > > > >
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