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 5FEBB36E489 for ; Thu, 21 May 2026 22:12:00 +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=1779401522; cv=none; b=iDnPwozawvSAfhGc2SXu/R6UHrl0nzdSxd/wLF6fqiJpSNQBWltJbwdTc2C4qBYPbEmuSe0qCJwNySQO5+jD2CsU/U5qzlfsLKVgXaZCEntndmQB74lbD47fW0Jg8oQonAoFaV2GQcBcZlPB3LyjzdzBMIt6UxEjJ+zIcsHB/GM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779401522; c=relaxed/simple; bh=A9ah0RgMfOidz5z7nkdG4Mwg2UwD6V86iSpbtMSeD1w=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=f3uobcSyM34AEEs8eeEqdl0UhQsucXeTRYjAUid9PAbGsKa7WW1mDRf1R7hlBrzQV0EXxPXw1VRCauOw7alUj1oUrKHLF3PIRLjMcGUAx6Kj7RacJuEVKwUgkj+nhwZKtlKF5/rDAJycdhOVvbHX3pMDumv1/bqH27tOxJPnSM8= 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=Qukz5zyU; 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="Qukz5zyU" Received: from administrator-PowerEdge-R660.corp.microsoft.com (unknown [131.107.147.7]) by linux.microsoft.com (Postfix) with ESMTPSA id 376F120B7167; Thu, 21 May 2026 15:11:52 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 376F120B7167 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1779401512; bh=5edBK/N/MRvo0l8pw3uQHEpk9bR+/l7DSu1rr7MICeM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Qukz5zyUi7gKJR0TmZCrR9aevV0UmLnBqvbbIIymzzda0yVRSqoC8fx3IhKMkWQ0K jfjRtgEDDtYLYi5ZxY3i8Nhaeo6qoLmguLeyYFnS++3AdOgnJ12MwZyL3okmZumu46 wgA95fJDaXl1xVOqiDxeuSxN8MK+ohEJk/SI+gTY= 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 , Baolu Lu Cc: Saurabh Sengar , skhawaja@google.com, pasha.tatashin@soleen.com, Will Deacon , Jacob Pan Subject: [PATCH v6 5/7] vfio: Enable cdev noiommu mode under iommufd Date: Thu, 21 May 2026 15:11:52 -0700 Message-ID: <20260521221155.1375144-6-jacob.pan@linux.microsoft.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260521221155.1375144-1-jacob.pan@linux.microsoft.com> References: <20260521221155.1375144-1-jacob.pan@linux.microsoft.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Now that devices under noiommu mode can bind with IOMMUFD and perform IOAS operations, lift restrictions on cdev from VFIO side. Use cases are documented in Documentation/driver-api/vfio.rst Signed-off-by: Jacob Pan --- v6: - Revert back to unified VFIO_NOIOMMU Kconfig for both cdev and group. Use Kconfig dependency to restrict usages and avoid null group checks. (Alex & Yi) - Add CAP_SYS_RAWIO checks for cdev open to maintain security parity with the group noiommu path. (Alex) v5: - Add Kconfig VFIO_CDEV_NOIOMMU to select IOMMUFD_NOIOMMU and its dependencies - Add comment to explain vfio_noiommu conditional definition (Alex) - Removed early return for group noiommu in bind/unbind - Use consistent wording referring to VFIO noiommu mode (Kevin) - Update unsafe_noiommu Kconfig help text (Kevin) - Change dev_warn to dev_info for noiommu enabling msg (Kevin) v4: - Remove early return in iommufd_bind for noiommu (Alex) v3: - Consolidate into fewer patches v2: - removed unnecessary device->noiommu set in iommufd_vfio_compat_ioas_get_id() Signed-off-by: Jacob Pan --- drivers/vfio/Kconfig | 8 +++++--- drivers/vfio/device_cdev.c | 3 +++ drivers/vfio/iommufd.c | 6 +++--- drivers/vfio/vfio.h | 20 +++++++++++++------- drivers/vfio/vfio_main.c | 23 +++++++++++++++++++---- include/linux/vfio.h | 1 + 6 files changed, 44 insertions(+), 17 deletions(-) diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig index ceae52fd7586..d3d8fef2855c 100644 --- a/drivers/vfio/Kconfig +++ b/drivers/vfio/Kconfig @@ -22,8 +22,7 @@ config VFIO_DEVICE_CDEV The VFIO device cdev is another way for userspace to get device access. Userspace gets device fd by opening device cdev under /dev/vfio/devices/vfioX, and then bind the device fd with an iommufd - to set up secure DMA context for device access. This interface does - not support noiommu. + to set up secure DMA context for device access. If you don't know what to do here, say N. @@ -62,7 +61,10 @@ endif config VFIO_NOIOMMU bool "VFIO No-IOMMU support" - depends on VFIO_GROUP + depends on VFIO_GROUP || VFIO_DEVICE_CDEV + depends on !VFIO_GROUP || VFIO_CONTAINER || IOMMUFD_VFIO_CONTAINER + depends on !VFIO_DEVICE_CDEV || !GENERIC_ATOMIC64 + select IOMMUFD_NOIOMMU if VFIO_DEVICE_CDEV help VFIO is built on the ability to isolate devices using the IOMMU. Only with an IOMMU can userspace access to DMA capable devices be diff --git a/drivers/vfio/device_cdev.c b/drivers/vfio/device_cdev.c index 54abf312cf04..4e2c1e4fc1f8 100644 --- a/drivers/vfio/device_cdev.c +++ b/drivers/vfio/device_cdev.c @@ -27,6 +27,9 @@ int vfio_device_fops_cdev_open(struct inode *inode, struct file *filep) struct vfio_device_file *df; int ret; + if (device->noiommu && !capable(CAP_SYS_RAWIO)) + return -EPERM; + /* Paired with the put in vfio_device_fops_release() */ if (!vfio_device_try_get_registration(device)) return -ENODEV; diff --git a/drivers/vfio/iommufd.c b/drivers/vfio/iommufd.c index a38d262c6028..d4f2e2a0f2f3 100644 --- a/drivers/vfio/iommufd.c +++ b/drivers/vfio/iommufd.c @@ -25,8 +25,8 @@ int vfio_df_iommufd_bind(struct vfio_device_file *df) lockdep_assert_held(&vdev->dev_set->lock); - /* Returns 0 to permit device opening under noiommu mode */ - if (vfio_device_is_noiommu(vdev)) + /* Group noiommu via iommufd compat needs no device binding */ + if (df->group && vfio_device_is_noiommu(vdev)) return 0; return vdev->ops->bind_iommufd(vdev, ictx, &df->devid); @@ -58,7 +58,7 @@ void vfio_df_iommufd_unbind(struct vfio_device_file *df) lockdep_assert_held(&vdev->dev_set->lock); - if (vfio_device_is_noiommu(vdev)) + if (df->group && vfio_device_is_noiommu(vdev)) return; if (vdev->ops->unbind_iommufd) diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h index e4b72e79b7e3..6f0a2dfc8a00 100644 --- a/drivers/vfio/vfio.h +++ b/drivers/vfio/vfio.h @@ -358,19 +358,13 @@ void vfio_init_device_cdev(struct vfio_device *device); static inline int vfio_device_add(struct vfio_device *device) { - /* cdev does not support noiommu device */ - if (vfio_device_is_noiommu(device)) - return device_add(&device->device); vfio_init_device_cdev(device); return cdev_device_add(&device->cdev, &device->device); } static inline void vfio_device_del(struct vfio_device *device) { - if (vfio_device_is_noiommu(device)) - device_del(&device->device); - else - cdev_device_del(&device->cdev, &device->device); + cdev_device_del(&device->cdev, &device->device); } int vfio_device_fops_cdev_open(struct inode *inode, struct file *filep); @@ -420,6 +414,18 @@ static inline void vfio_cdev_cleanup(void) } #endif /* CONFIG_VFIO_DEVICE_CDEV */ +#if IS_ENABLED(CONFIG_VFIO_NOIOMMU) +static inline bool vfio_device_is_cdev_noiommu(struct vfio_device *vdev) +{ + return vdev->noiommu; +} +#else +static inline bool vfio_device_is_cdev_noiommu(struct vfio_device *vdev) +{ + return false; +} +#endif + #if IS_ENABLED(CONFIG_VFIO_VIRQFD) int __init vfio_virqfd_init(void); void vfio_virqfd_exit(void); diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c index 6222376ab6ab..84381c500623 100644 --- a/drivers/vfio/vfio_main.c +++ b/drivers/vfio/vfio_main.c @@ -321,6 +321,20 @@ static int vfio_init_device(struct vfio_device *device, struct device *dev, return ret; } +static int vfio_device_set_noiommu_and_name(struct vfio_device *device) +{ + if (IS_ENABLED(CONFIG_VFIO_DEVICE_CDEV) && vfio_noiommu && !device->dev->iommu) { + device->noiommu = true; + add_taint(TAINT_USER, LOCKDEP_STILL_OK); + dev_warn(device->dev, + "Adding kernel taint for vfio-noiommu cdev on device\n"); + } + + /* Just to be safe, expose to user explicitly noiommu cdev node */ + return dev_set_name(&device->device, "%svfio%d", + device->noiommu ? "noiommu-" : "", device->index); +} + static int __vfio_register_dev(struct vfio_device *device, enum vfio_group_type type) { @@ -340,20 +354,21 @@ static int __vfio_register_dev(struct vfio_device *device, if (!device->dev_set) vfio_assign_device_set(device, device); - ret = dev_set_name(&device->device, "vfio%d", device->index); + ret = vfio_device_set_group(device, type); if (ret) return ret; - ret = vfio_device_set_group(device, type); + ret = vfio_device_set_noiommu_and_name(device); if (ret) - return ret; + goto err_out; /* * VFIO always sets IOMMU_CACHE because we offer no way for userspace to * restore cache coherency. It has to be checked here because it is only * valid for cases where we are using iommu groups. */ - if (type == VFIO_IOMMU && !vfio_device_is_noiommu(device) && + if (type == VFIO_IOMMU && !(vfio_device_is_noiommu(device) || + vfio_device_is_cdev_noiommu(device)) && !device_iommu_capable(device->dev, IOMMU_CAP_CACHE_COHERENCY)) { ret = -EINVAL; goto err_out; diff --git a/include/linux/vfio.h b/include/linux/vfio.h index 31b826efba00..45f08986359e 100644 --- a/include/linux/vfio.h +++ b/include/linux/vfio.h @@ -74,6 +74,7 @@ struct vfio_device { u8 iommufd_attached:1; #endif u8 cdev_opened:1; + u8 noiommu:1; /* * debug_root is a static property of the vfio_device * which must be set prior to registering the vfio_device. -- 2.43.0