Re: Xen 3.3: Problem HVM guest

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Thu, Aug 14, 2008 at 07:10:25PM +0200, Christoph Egger wrote:
> On Thursday 14 August 2008 19:05:08 Manuel Bouyer wrote:
> > On Thu, Aug 14, 2008 at 06:57:15PM +0200, Christoph Egger wrote:
> > > > OK, so 0x9c1ff167 is really the complete pte value. This would make it
> > > > point to a physical address at 2497MB. Do you have that much memory in
> > > > this box ?
> > >
> > > Yes. It has 4GB.
> >
> > OK, so we have a valid pte entry, pointing to valid memory, for the
> > affected VA; yet writing to the VA seems to cause a fault. The only
> > remaining issue I can see is that we would be updating the wrong pmap.
> > but I can't see how it could happen for this case, and not for the
> > other IOCTL_PRIVCMD_MMAP users ...
> 
> The machine is a Dual-Core CPU machine. Since NetBSD/Xen (= Dom0)
> utilizes only the BSP due to lack of SMP support, it is very likely the
> guest utilizes the other CPU core.
> Does this help?

Not really, as the write which is failing is also in dom0 (so on the same
CPU). I think the tlb should be properly invalidated. Just to make sure
you can try adding
pmap_tlb_shootdown(pmap, va, 0, opte);
just after xpq_update_foreign() in pmap_enter_ma(). But as we're
switching pmaps on return to userland, this shouldn't be needed.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--