Re: cleaning up NMI handling in trap()

[David Young <dyoung%pobox.com@localhost>]

On Sat, Mar 19, 2011 at 12:09:13PM +0100, Manuel Bouyer wrote:
> On Fri, Mar 18, 2011 at 05:02:29PM -0500, David Young wrote:
> > On Fri, Mar 18, 2011 at 09:50:10PM +0100, Manuel Bouyer wrote:
> > > nmi_dispatch() is not available for xen; but it's now called
> > > inconditionally from trap(). Did you forget to add a dummy
> > > implementation for XEN ?
> > 
> > I added it to the xen kernel build.  Is there some reason it will not
> > work on xen?
> 
> I guess I missed this from your patch. Well, it'll probably never be
> called on Xen, as the hypervisor will catch it and will probably panic
> itself.

I hope that it doesn't panic the hypervisor!  Another developer's desire
to force a NetBSD DomU into ddb by sending an NMI with 'xm nmi' is what
set me down this path. :-)

Does the hypervisor provide some other channel for notifying a DomU
of exceptions with high priority?  Maybe NMI is only intended to be
available to HVM guests.  When PCI pass-through is used, I wonder if
there is a Xen-specific channel for telling guests, "PCI SERR# asserted
on bus 0".

Dave

-- 
David Young             OJC Technologies
dyoung%ojctech.com@localhost      Urbana, IL * (217) 344-0444 x24