RE: [Xen-devel] Task Switching and Xen-SVM

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

> > > Do you actually know of any (32-bit) OS that uses task switching?
> >
> > It's often used in double fault, NMI and MCA handlers, all of
> > which are
> > typically fatal.
> >
> > It would still be good to have them implemented to get a decent oops
> > message out though.
> 
> NMI and MCA shouldn't happen in the guest - at least not in the
current
> architecture where NMI and MCA are all handled in Xen. Is there a
> reasonable cause for this to change anytime soon? [How do we know what
> guest cause MCE - as memory related MCE's happen on the processor
owning
> the memory, and may also be caused by the "memory scrubber". And it
> doesn't really make much sense to give MCE's to the guest, as it's
> generally a hardware related problem.]
> 
> NMI's to guest may make more sense if we take for example performance
> counters... Not sure if this is important or not... Performance
counting
> in the guest is another "interesting" topic where it's hard for the
> guest to make sense of the numbers without knowing about the
hypervisor,
> I think...

Well, having the s/w equivalent of the NMI 'dump' button would be
useful. 

Ian

 
> --
> Mats
> >
> > Ian
> >
> > > In my
> > > experience, it's horribly slow (because it generally
saves/restores
> > more
> > > of the context than is necessary). Of course, in 64-bit
> > mode it's not
> > > even allowed, all task-management features have been removed...
I'm
> > > saying 32-bit OS, since there's probably some 16-bit OS's out
there
> > that
> > > do use task-switching, but those OS's are not able to run on
current
> > Xen
> > > anyways, since Xen in it's current form is very poor at supporting
> > > segments with base != 0 in protected mode. So far I've only
> > seen a few
> > > rare reports of anyone actually wishing to run a 16-bit OS...
> > >
> > > --
> > > Mats
> > > >
> > > > Thanks,
> > > > Vivek
> > > >
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> > > > http://lists.xensource.com/xen-devel
> > > >
> > > >
> > > >
> > >
> > >
> > >
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> >
> >
> >
> 


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