question on "powerpc/pseries/dma: Allow SWIOTLB"

Christoph Hellwig hch at
Fri Jul 19 18:05:32 AEST 2019

On Fri, Jul 19, 2019 at 06:00:25PM +1000, Alexey Kardashevskiy wrote:
> > But shouldn't we force usage of the direct ops in that case as the
> > IOMMU is not neededed at all?
> We do, for mappings, but not unmappings and syncing.

Well, I mean as in literally not setting a dma_ops so that the
dma_direct code is used without the indirection through the iommu ops.
This is not only more obvious, but also faster as you avoid the
indirect call (although that probably doesn't matter much if you
are bounce buffering anyway).

> > Also isn't that support non-upstream so far?
> How is this relevant? I expect the existing "swiotlb=force" just work.

I though the whole secure VM support was still not upstream.

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