Re: Question about iommu on x86_64 and radeon driver.

[Daniel Haid]

> Only if you allow 3GB or less in the machine. So you would have to do
> mem=3G as well.
>
> The reason is that (and you can see that yourself by looking at the
> E820), is that 1GB is actually _above_ the 4GB.

Just another question on this one:

Why can a driver not simply ask for DMA-capable memory, is this not
what memory zones are for?

So if a driver wants to do DMA it requests DMA-memory and gets it from
the lower than 4GB address space.

But for some reason it is not done like this, why?
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