Dave Jones 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.
Do you have bug numbers at hand?
Searching for CONFIG_DMAR gives me "Zarro Boogs found".
Maybe it's been improved enough to tolerate them, so we can
give it a spin in rawhide for a while to see what happens.
Well, it works for me. Single test box only though. As the machine in
question actually has memory above 4G it is a nice speedup for kernel
builds (sys time going down from ~15min to ~5min).