linux-kernel - [PATCH 0/3] iommu/vt-d: Add support to hitless replace IOMMU domain

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Message-ID: <20260107201800.2486137-1-skhawaja@google.com>
Date: Wed,  7 Jan 2026 20:17:57 +0000
From: Samiullah Khawaja <skhawaja@...gle.com>
To: David Woodhouse <dwmw2@...radead.org>, Lu Baolu <baolu.lu@...ux.intel.com>, 
	Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>, 
	Pasha Tatashin <pasha.tatashin@...een.com>, Jason Gunthorpe <jgg@...pe.ca>, 
	David Matlack <dmatlack@...gle.com>
Cc: Samiullah Khawaja <skhawaja@...gle.com>, Robin Murphy <robin.murphy@....com>, 
	Pratyush Yadav <pratyush@...nel.org>, Kevin Tian <kevin.tian@...el.com>, 
	Alex Williamson <alex@...zbot.org>, Shuah Khan <shuah@...nel.org>, iommu@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
	Saeed Mahameed <saeedm@...dia.com>, Adithya Jayachandran <ajayachandra@...dia.com>, 
	Parav Pandit <parav@...dia.com>, Leon Romanovsky <leonro@...dia.com>, William Tu <witu@...dia.com>
Subject: [PATCH 0/3] iommu/vt-d: Add support to hitless replace IOMMU domain

Intel IOMMU Driver already supports replacing IOMMU domain hitlessly in
scalable mode. The support is not available in legacy mode and for
NO_PASID in scalable mode. This patch series adds the support for legacy
mode and NO_PASID scalable mode.

This is needed for the Live update IOMMU persistence to hotswap the
iommu domain after liveupdate:
https://lore.kernel.org/all/20251202230303.1017519-1-skhawaja@google.com/

The patch adds the support for scalable mode NO_PASID mode by using the
existing replace semantics. This works since in scalable mode the
context entries are not updated and only the pasid entries are updated.

The patch series also contains a vfio selftests for the iommu domain
replace using iommufd hwpt replace functionality.

Tested on a Host with scalable mode and on Qemu with legacy mode:

tools/testing/selftests/vfio/scripts/setup.sh <dsa_device_bdf>
tools/testing/selftests/vfio/vfio_iommufd_hwpt_replace_test <dsa_device_bdf>

TAP version 13
1..2
# Starting 2 tests from 2 test cases.
#  RUN           vfio_iommufd_replace_hwpt_test.domain_replace.memcpy ...
#            OK  vfio_iommufd_replace_hwpt_test.domain_replace.memcpy
ok 1 vfio_iommufd_replace_hwpt_test.domain_replace.memcpy
#  RUN           vfio_iommufd_replace_hwpt_test.noreplace.memcpy ...
#            OK  vfio_iommufd_replace_hwpt_test.noreplace.memcpy
ok 2 vfio_iommufd_replace_hwpt_test.noreplace.memcpy
# PASSED: 2 / 2 tests passed.
# Totals: pass:2 fail:0 xfail:0 xpass:0 skip:0 error:0

Samiullah Khawaja (3):
  iommu/vt-d: Allow replacing no_pasid iommu_domain
  vfio: selftests: Add support of creating iommus from iommufd
  vfio: selftests: Add iommufd hwpt replace test

 drivers/iommu/intel/iommu.c                   | 107 +++++++++----
 tools/testing/selftests/vfio/Makefile         |   1 +
 .../vfio/lib/include/libvfio/iommu.h          |   2 +
 .../lib/include/libvfio/vfio_pci_device.h     |   2 +
 tools/testing/selftests/vfio/lib/iommu.c      |  60 ++++++-
 .../selftests/vfio/lib/vfio_pci_device.c      |  16 +-
 .../vfio/vfio_iommufd_hwpt_replace_test.c     | 151 ++++++++++++++++++
 7 files changed, 303 insertions(+), 36 deletions(-)
 create mode 100644 tools/testing/selftests/vfio/vfio_iommufd_hwpt_replace_test.c


base-commit: 6cd6c12031130a349a098dbeb19d8c3070d2dfbe
-- 
2.52.0.351.gbe84eed79e-goog