From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id DC66C37F00D for ; Tue, 14 Apr 2026 21:14:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776201256; cv=none; b=CQeUtb1rxdDxen+02AqrTFjzhnKNlqx2qIoPbQ31Zw/pDBQMfR+auEUA8FDInD+kay2E1VVupJW2qRk332db6UqmGEiMVP3MDaV2Ly68Xq4yeB4pbhJaTpfu1EIHhjKZ6fVhDW/KrXPMvlqGFnqMVgLnUS5Jm/mLL+LmVTVegWg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776201256; c=relaxed/simple; bh=a03dfvBDnjCIeZxAl25YvfWZamrx0OHLwY0Hdpk5i5I=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=dACU90gjdeB58BnlPpgnIUyqvoWzW+boRyedwf/I2RW+Wwxa2Zw418w1ueQlutPmAstXIkqY1s208N4O9Pm3nM/JRV3omdWR9BL7Bu48tI2HizJhOx6Dt2n6zHV6Sn7n39JyfTIXK0CqGbnSGYh2YM12EVH+vAzrEyboEZP1J1c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=bl96z0C3; arc=none smtp.client-ip=13.77.154.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="bl96z0C3" Received: from DESKTOP-0403QTC.corp.microsoft.com (unknown [20.191.74.188]) by linux.microsoft.com (Postfix) with ESMTPSA id 1EED420B6F01; Tue, 14 Apr 2026 14:14:14 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 1EED420B6F01 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1776201254; bh=J+x8M7kZoay7wmXk4X4HYJDWsyg39BlXt9aAiFwn3cI=; h=From:To:Cc:Subject:Date:From; b=bl96z0C3FeLlAuOoURC7jEtKeWzagbS3K2HEKHX6qPraFT42UCamKNUIxSOoZBYaC Mm4n156z8pvcgNaiy8Koa+ErPgEVTnNuTIWM3HcZTXI1FHzkL9DRgMDMys3sdpXWgP qgrc8VKfRhNyLAnib1uXvcKjUkr45dPzzxS5/4xg= From: Jacob Pan To: linux-kernel@vger.kernel.org, "iommu@lists.linux.dev" , Jason Gunthorpe , Alex Williamson , Joerg Roedel , Mostafa Saleh , David Matlack , Robin Murphy , Nicolin Chen , "Tian, Kevin" , Yi Liu Cc: skhawaja@google.com, pasha.tatashin@soleen.com, Will Deacon , Jacob Pan , Baolu Lu Subject: [PATCH V4 00/10] iommufd: Enable noiommu mode for cdev Date: Tue, 14 Apr 2026 14:14:02 -0700 Message-Id: <20260414211412.2729-1-jacob.pan@linux.microsoft.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 support No-IOMMU mode, which is the purpose of this patch. In summary, we have: |-------------------------+------+---------------| | Device access mode | VFIO | IOMMUFD | |-------------------------+------+---------------| | group /dev/vfio/$GROUP | Yes | Yes | |-------------------------+------+---------------| | cdev /dev/vfio/devices/ | No | This patch | |-------------------------+------+---------------| Beyond enabling cdev for IOMMUFD, this patch also addresses the following deficiencies in the current No-IOMMU mode suggested by Jason[1]: - Devices operating under No-IOMMU mode are limited to device-level UAPI access, without container or IOAS-level capabilities. Consequently, user-space drivers lack structured mechanisms for page pinning and often resort to mlock(), which is less robust than pin_user_pages() used for devices backed by a physical IOMMU. For example, mlock() does not prevent page migration. - There is no architectural mechanism for obtaining physical addresses for DMA. As a workaround, user-space drivers frequently rely on /proc/pagemap tricks or hardcoded values. By allowing noiommu device access to IOMMUFD IOAS and HWPT objects, this patch brings No-IOMMU mode closer to full citizenship within the IOMMU subsystem. In addition to addressing the two deficiencies mentioned above, the expectation is that it will also enable No-IOMMU devices to seamlessly participate in live update sessions via KHO [2]. Furthermore, these devices will use the IOMMUFD-based ownership checking model for VFIO_DEVICE_PCI_HOT_RESET, eliminating the need for an iommufd_access object as required in a previous attempt [3]. ChangeLog: V4: - Fix various corner cases pointed out by (Sashiko) Details in each patch changelog. V3: - Improve error handling [3/10] (Mostafa) - Simplify vfio_device_is_noiommu logic and merged in [6/10] (Mostafa) - Fix build dependency on !GENERIC_ATOMIC64 - Add comment to explain the design difference over the legacy noiommu VFIO code.[1/10] V2: - Fix build depenency by adding IOMMU_SUPPORT in [8/11] - Add an optimization to scan beyond the first page for a contiguous physical address range and return its length instead of a single page.[4/11] Since RFC[4]: - Abandoned dummy iommu driver approach as patch 1-3 absorbed the changes into iommufd. [1] https://lore.kernel.org/linux-iommu/20250603175403.GA407344@nvidia.com/ [2] https://lore.kernel.org/linux-pci/20251027134430.00007e46@linux.microsoft.com/ [3] https://lore.kernel.org/kvm/20230522115751.326947-1-yi.l.liu@intel.com/ [4] https://lore.kernel.org/linux-iommu/20251201173012.18371-1-jacob.pan@linux.microsoft.com/ Thanks, Jacob Jacob Pan (7): iommufd: Add an ioctl IOMMU_IOAS_GET_PA to query PA from IOVA vfio: Allow null group for noiommu without containers vfio: Introduce and set noiommu flag on vfio_device vfio: Enable cdev noiommu mode under iommufd vfio:selftest: Handle VFIO noiommu cdev selftests/vfio: Add iommufd noiommu mode selftest for cdev Documentation: Update VFIO NOIOMMU mode Jason Gunthorpe (3): iommufd: Support a HWPT without an iommu driver for noiommu iommufd: Move igroup allocation to a function iommufd: Allow binding to a noiommu device Documentation/driver-api/vfio.rst | 45 +- drivers/iommu/iommufd/Makefile | 1 + drivers/iommu/iommufd/device.c | 175 ++++-- drivers/iommu/iommufd/hw_pagetable.c | 11 +- drivers/iommu/iommufd/hwpt_noiommu.c | 102 ++++ drivers/iommu/iommufd/io_pagetable.c | 60 ++ drivers/iommu/iommufd/ioas.c | 25 + drivers/iommu/iommufd/iommufd_private.h | 5 + drivers/iommu/iommufd/main.c | 3 + drivers/vfio/Kconfig | 8 +- drivers/vfio/group.c | 41 +- drivers/vfio/iommufd.c | 7 - drivers/vfio/vfio.h | 28 +- drivers/vfio/vfio_main.c | 12 +- include/linux/vfio.h | 10 + include/uapi/linux/iommufd.h | 25 + tools/testing/selftests/vfio/Makefile | 1 + .../lib/include/libvfio/vfio_pci_device.h | 1 + .../selftests/vfio/lib/vfio_pci_device.c | 32 +- .../vfio/vfio_iommufd_noiommu_test.c | 567 ++++++++++++++++++ .../vfio/vfio_pci_liveupdate_kexec_test.c | 9 + 21 files changed, 1074 insertions(+), 94 deletions(-) create mode 100644 drivers/iommu/iommufd/hwpt_noiommu.c create mode 100644 tools/testing/selftests/vfio/vfio_iommufd_noiommu_test.c -- 2.34.1