Re: [PATCH 12/12] swiotlb-xen: this is PV-only on x86

[Christoph Hellwig]

On Tue, Sep 07, 2021 at 02:13:21PM +0200, Jan Beulich wrote:
> The code is unreachable for HVM or PVH, and it also makes little sense
> in auto-translated environments. On Arm, with
> xen_{create,destroy}_contiguous_region() both being stubs, I have a hard
> time seeing what good the Xen specific variant does - the generic one
> ought to be fine for all purposes there. Still Arm code explicitly
> references symbols here, so the code will continue to be included there.

Can the Xen/arm folks look into that?  Getting ARM out of using
swiotlb-xen would be a huge step forward cleaning up some DMA APIs.

> 
> Instead of making PCI_XEN's "select" conditional, simply drop it -
> SWIOTLB_XEN will be available unconditionally in the PV case anyway, and
> is - as explained above - dead code in non-PV environments.
> 
> This in turn allows dropping the stubs for
> xen_{create,destroy}_contiguous_region(), the former of which was broken
> anyway - it failed to set the DMA handle output.

Looks good:

Reviewed-by: Christoph Hellwig <hch@xxxxxx>