linux-kernel - Re: [PATCH] vfio: selftests: Add vfio_dma_mapping_mmio

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Message-ID: <20260108183339.GF545276@ziepe.ca>
Date: Thu, 8 Jan 2026 14:33:39 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: David Matlack <dmatlack@...gle.com>
Cc: Alex Williamson <alex@...zbot.org>, Alex Mastro <amastro@...com>,
	Shuah Khan <shuah@...nel.org>, Peter Xu <peterx@...hat.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH] vfio: selftests: Add vfio_dma_mapping_mmio_test

On Thu, Jan 08, 2026 at 10:24:19AM -0800, David Matlack wrote:
> > > Oh, I was thinking about a compatability only flow only in the type 1
> > > emulation that internally magically converts a VMA to a dmabuf, but I
> > > haven't written anything.. It is a bit tricky and the type 1 emulation
> > > has not been as popular as I expected??
> >
> > In part because of this gap, I'd guess.  Thanks,
> 
> Lack of huge mappings in the IOMMU when using VFIO_TYPE1_IOMMU is
> another gap I'm aware of.
> vfio_dma_mapping_test.vfio_type1_iommu_anonymous_hugetlb_1gb.dma_map_unmap
> fails when IOMMUFD_VFIO_CONTAINER is enabled.

What is this? I'm not aware of it..

> Is the plan to address all the gaps so IOMMUFD_VFIO_CONTAINER can be
> made the default and the type1 code can be dropped from the upstream
> kernel?

This was a dream for sure, distros can decide if they want to continue
to support both or have an option to do just one.

Jason