linux-kernel - Re: [RFC 0/8] iommufd: Enable noiommu mode for cdev

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Message-ID: <20260130193529.GJ2223369@nvidia.com>
Date: Fri, 30 Jan 2026 15:35:29 -0400
From: Jason Gunthorpe <jgg@...dia.com>
To: Jacob Pan <jacob.pan@...ux.microsoft.com>
Cc: linux-kernel@...r.kernel.org,
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	Alex Williamson <alex.williamson@...hat.com>,
	Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
	Robin Murphy <robin.murphy@....com>,
	Nicolin Chen <nicolinc@...dia.com>,
	"Tian, Kevin" <kevin.tian@...el.com>,
	"Liu, Yi L" <yi.l.liu@...el.com>, skhawaja@...gle.com,
	pasha.tatashin@...een.com, Zhang Yu <zhangyu1@...ux.microsoft.com>,
	Jean Philippe-Brucker <jean-philippe@...aro.org>,
	David Matlack <dmatlack@...gle.com>
Subject: Re: [RFC 0/8] iommufd: Enable noiommu mode for cdev

On Mon, Dec 01, 2025 at 09:30:04AM -0800, Jacob Pan wrote:
> VFIO's unsafe_noiommu_mode has long provided a way for userspace drivers
> to operate on platforms lacking a hardware IOMMU. Today, IOMMUFD also
> supports No-IOMMU mode for group based devices under vfio_compat mode.
> However, IOMMUFD's native character device (cdev) does not yet implement
> No-IOMMU mode, which is the purpose of this patch. In summary, we have:

I tried to build this without the fake iommu driver and it worked out OK:

https://github.com/jgunthorpe/linux/commits/iommufd_noiommu/

Needs a little more checking than I might have done, but can you take
that and try for a submission?

Thanks,
Jason