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 51D0A296BCF for ; Thu, 12 Mar 2026 15:56:39 +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=1773331001; cv=none; b=td0XBnEKp1IBBCSUrklwXnMd+/xh8lWmVSMBVEBmp7XGF1p9qhJDxlOi6ADp7cVFfUyjivITgheO4DKfvlVMw8XBnzWUwQp8T+LKXx7Sk7qieq3mn3d60vX7yGy325ZxKh84PJNf1CW4uy2Tc5l6esW7oG85jV7eYVYuB/W32KA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773331001; c=relaxed/simple; bh=xTe2BzjMPS4UnZWGU4LrDZ7RUuuOo3XqGTNdvfBAs1g=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=rk2NTJ0OShkd+U82xYJBnNsbW0YTj5AnSaoCFjsDsQg+LeXrifwP0C/kmAap3RwUga/A86NrW8VAGP3PAiFZpj+w56hiJzkkg9Hoj2dorQtasoRXA4YEIKzSlzYd9G5OKxZCSfUU2QvIHWSUd/XlUV1ZfXK7pGv83OCPFcp4r4E= 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=evYI8LlL; 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="evYI8LlL" Received: from DESKTOP-0403QTC.corp.microsoft.com (unknown [52.148.138.235]) by linux.microsoft.com (Postfix) with ESMTPSA id 640F820B6F01; Thu, 12 Mar 2026 08:56:38 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 640F820B6F01 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1773330998; bh=tppXY63rULxtStB4G+4JP/DOV6TA7Tk95wQk5wUhccw=; h=From:To:Cc:Subject:Date:From; b=evYI8LlLvQZYK0ChBYSszMMKHlEwWJ2mYeg0JEWGl9NzD1+943tD0EiXyB3MezF2y VR7JmFzM+RT4SMnuf+q9KsjY34fAQuhLvPJOmxeHS/YijxfOVtWkpYCgL34L4f1AhT 8kkyKnVPQRvjZMujonVJvV/v20s3IlNFa08UdNAo= From: Jacob Pan To: linux-kernel@vger.kernel.org, "iommu@lists.linux.dev" , Jason Gunthorpe , Alex Williamson , Joerg Roedel , 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 V2 00/11] iommufd: Enable noiommu mode for cdev Date: Thu, 12 Mar 2026 08:56:26 -0700 Message-Id: <20260312155637.376854-1-jacob.pan@linux.microsoft.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: iommu@lists.linux.dev 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: 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 (8): 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: Update noiommu device detection logic for cdev vfio: Enable cdev noiommu mode under iommufd vfio:selftest: Handle VFIO noiommu cdev selftests/vfio: Add iommufd noiommu mode selftest for cdev Doc: 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 | 44 +- drivers/iommu/iommufd/Makefile | 1 + drivers/iommu/iommufd/device.c | 161 +++-- drivers/iommu/iommufd/hw_pagetable.c | 11 +- drivers/iommu/iommufd/hwpt_noiommu.c | 91 +++ drivers/iommu/iommufd/io_pagetable.c | 60 ++ drivers/iommu/iommufd/ioas.c | 28 + drivers/iommu/iommufd/iommufd_private.h | 5 + drivers/iommu/iommufd/main.c | 3 + drivers/vfio/Kconfig | 7 +- drivers/vfio/group.c | 35 +- drivers/vfio/iommufd.c | 7 - drivers/vfio/vfio.h | 34 +- drivers/vfio/vfio_main.c | 22 +- include/linux/vfio.h | 10 + include/uapi/linux/iommufd.h | 25 + tools/testing/selftests/vfio/Makefile | 1 + .../selftests/vfio/lib/vfio_pci_device.c | 25 +- .../vfio/vfio_iommufd_noiommu_test.c | 549 ++++++++++++++++++ 19 files changed, 1027 insertions(+), 92 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