config changes

[David Woodhouse]

On Tue, 2009-01-13 at 13:39 -0800, Chris Wright wrote:
> * Dave Jones (davej at redhat.com) wrote:
> > On Tue, Jan 13, 2009 at 09:55:27PM +0100, Gerd Hoffmann wrote:
> >  > Bill Nottingham wrote:
> >  > > Here's some proposed config changes.
> >  > 
> >  > Jumping on the wagon ;)
> >  > 
> >  > Can we enable CONFIG_DMAR please?  This turns on the IOMMU on intel
> >  > boxes, using VT-d.  Called "DMA Remapping" in intel speak, this is where
> >  > the config option name comes from.  Advantages:
> >  > 
> >  >   (1) 32bit PCI devices can DMA to memory above 4G, thus the need for
> >  >       swiotlb (i.e. bounce buffers) is gone.
> >  >   (2) It allows kvm to pass through PCI devices to guests securely.
> >  
> > The last time we tried this, it blew up a lot due to broken BIOSes.
> > Maybe it's been improved enough to tolerate them, so we can probably
> > give it a spin in rawhide for a while to see what happens.
> 
> Upstream was still broken as recently as Friday for bad BIOSes (x200s in
> this case).  Wonder if opt-in via cmdline would be helpful?

This is now believed to be fixed, and I've re-enabled DMAR in rawhide.

I see Chuck has applied the fix to F-10 already, and we'll look at the
question of re-enabling DMAR there later. For now you still need to boot
F-10 with 'intel_iommu=on'.

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse at intel.com                              Intel Corporation