Re: [RFC 2/3] iommu: Account for dma_mask and iommu aperture in IOVA reserved regions

[Christoph Hellwig]

On Mon, Sep 28, 2020 at 09:50:36PM +0200, Eric Auger wrote:
> VFIO currently exposes the usable IOVA regions through the
> VFIO_IOMMU_GET_INFO ioctl. However it fails to take into account
> the dma_mask of the devices within the container. The top limit
> currently is defined by the iommu aperture.

Can we take a step back here?  The dma_mask only has a meaning for
the DMA API, and not the iommu API, it should have no relevance here.

More importantly if we are using vfio no dma_mask should be set to
start with.

> +		if (geo.aperture_end < ULLONG_MAX && geo.aperture_end != geo.aperture_start) {

Please avoid pointlessly overlong lines.