linux-kernel - Re: [RFC PATCH 06/21] vfio/pci: Accept live update preservation request for VFIO cdev

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Message-ID: <20251028132855.GJ760669@ziepe.ca>
Date: Tue, 28 Oct 2025 10:28:55 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Jacob Pan <jacob.pan@...ux.microsoft.com>
Cc: Vipin Sharma <vipinsh@...gle.com>, bhelgaas@...gle.com,
	alex.williamson@...hat.com, pasha.tatashin@...een.com,
	dmatlack@...gle.com, graf@...zon.com, pratyush@...nel.org,
	gregkh@...uxfoundation.org, chrisl@...nel.org, rppt@...nel.org,
	skhawaja@...gle.com, parav@...dia.com, saeedm@...dia.com,
	kevin.tian@...el.com, jrhilke@...gle.com, david@...hat.com,
	jgowans@...zon.com, dwmw2@...radead.org, epetron@...zon.de,
	junaids@...gle.com, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, kvm@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: Re: [RFC PATCH 06/21] vfio/pci: Accept live update preservation
 request for VFIO cdev

On Mon, Oct 27, 2025 at 01:44:30PM -0700, Jacob Pan wrote:
> I have a separate question regarding noiommu devices. I’m currently
> working on adding noiommu mode support for VFIO cdev under iommufd.

Oh how is that going? I was just thinking about that again..

After writing the generic pt self test it occured to me we now have
enough infrastructure for iommufd to internally create its own
iommu_domain with a AMDv1 page table for the noiommu devices. It would
then be so easy to feed that through the existing machinery and have
all the pinning/etc work.

Then only an ioctl to read back the physical addresses from this
special domain would be needed

It actually sort of feels pretty easy..

Jason