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Date:   Mon, 18 Oct 2021 13:32:38 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     David Gibson <david@gibson.dropbear.id.au>
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Subject: Re: [RFC 13/20] iommu: Extend iommu_at[de]tach_device() for multiple
 devices group
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On Mon, Oct 18, 2021 at 02:57:12PM +1100, David Gibson wrote:

> The first user might read this.  Subsequent users are likely to just
> copy paste examples from earlier things without fully understanding
> them.  In general documenting restrictions somewhere is never as
> effective as making those restrictions part of the interface signature
> itself.

I'd think this argument would hold more water if you could point to
someplace in existing userspace that cares about the VFIO grouping.

From what I see the applications do what the admin tells them to do -
and if the admin says to use a certain VFIO device then that is
excatly what they do. I don't know of any applications that ask the
admin to tell them group information.

What I see is aligning what the kernel provides to the APIs the
applications have already built.

Jason