RE: [Xen-devel] PoD in other (not GPLPV) drivers

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-devel-
> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of James Harper
> Sent: 03 March 2011 10:22
> To: George Dunlap
> Cc: George Dunlap; xen devel
> Subject: RE: [Xen-devel] PoD in other (not GPLPV) drivers
> 
> >
> > On Mon, 2011-02-28 at 22:20 +0000, James Harper wrote:
> > > Is there a way for DomU to get an interrupt when an unpopulated
> page
> > > is hit when the DomU has gone past its initial limit? That would
> > > allow me to at least write a message to the log and crash
> usefully
> > > if I can't do anything else about it.
> >
> > At the moment there's no mechanism for this.  Doing so would be a
> bit
> > tricky, as most of the places which do gfn_to_mfn() translations
> > aren't designed to handle failures gracefully (although that may
> have
> > changed since some of the guest paging stuff was introduced).
> >
> > If we were to do this at some point in the future, what do you
> think
> > you'd like the interface to look like?  (i.e., deliver NMI? MCE? a
> > different but well-known interrupt?  &c)
> >
> 
> I don't know that there is a sactioned way to intercept an NMI under
> windows.

KeRegisterNmiCallback()

See http://msdn.microsoft.com/en-us/library/ff553116%28v=vs.85%29.aspx

> An MCE would do the trick probably. Basically I want the
> user to know that their VM crashed because it hit the PoD limit,
> rather than have no idea why it crashed. Most of the time if a user
> gets a crash I ask for a copy of /var/log/xen/qemu-dm-<domu>.log, so
> if the message appeared there then that would be fine with me too.
> 
> I was under the impression that xen would blow the DomU up if it
> overstepped its PoD limit, but now I'm not so sure as I've seen
> windows BSoD with lots of different bug check codes when it happens.
> What should happen? I think that instant death is the only sensible
> outcome.
> 
> James
> 

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