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Date:   Mon, 18 Oct 2021 14:42:26 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     David Gibson <david@gibson.dropbear.id.au>
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Subject: Re: [RFC 11/20] iommu/iommufd: Add IOMMU_IOASID_ALLOC/FREE
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On Mon, Oct 18, 2021 at 02:50:54PM +1100, David Gibson wrote:

> Hrm... which makes me think... if we allow this for the common
> kernel-managed case, do we even need to have capcity in the high-level
> interface for reporting IO holes?  If the kernel can choose a non-zero
> base, it could just choose on x86 to place it's advertised window
> above the IO hole.

If the high level interface is like dma_map() then, no it doesn't need
the ability to report holes. Kernel would find and return the IOVA
from dma_map not accept it in.

Since dma_map is a well proven model I'm inclined to model the
simplied interface after it..

That said, if we have some ioctl 'query iova ranges' I would expect it
to work on an IOAS created by the simplified interface too.

Jason