Merge tag 'for-linus-iommufd' of git://git.kernel.org/pub/scm/linux/kernel/git/jgg/iommufd

Pull iommufd implementation from Jason Gunthorpe:
 "iommufd is the user API to control the IOMMU subsystem as it relates
  to managing IO page tables that point at user space memory.

  It takes over from drivers/vfio/vfio_iommu_type1.c (aka the VFIO
  container) which is the VFIO specific interface for a similar idea.

  We see a broad need for extended features, some being highly IOMMU
  device specific:
   - Binding iommu_domain's to PASID/SSID
   - Userspace IO page tables, for ARM, x86 and S390
   - Kernel bypassed invalidation of user page tables
   - Re-use of the KVM page table in the IOMMU
   - Dirty page tracking in the IOMMU
   - Runtime Increase/Decrease of IOPTE size
   - PRI support with faults resolved in userspace

  Many of these HW features exist to support VM use cases - for instance
  the combination of PASID, PRI and Userspace IO Page Tables allows an
  implementation of DMA Shared Virtual Addressing (vSVA) within a guest.
  Dirty tracking enables VM live migration with SRIOV devices and PASID
  support allow creating "scalable IOV" devices, among other things.

  As these features are fundamental to a VM platform they need to be
  uniformly exposed to all the driver families that do DMA into VMs,
  which is currently VFIO and VDPA"

For more background, see the extended explanations in Jason's pull request:

  https://lore.kernel.org/lkml/Y5dzTU8dlmXTbzoJ@nvidia.com/

* tag 'for-linus-iommufd' of git://git.kernel.org/pub/scm/linux/kernel/git/jgg/iommufd: (62 commits)
  iommufd: Change the order of MSI setup
  iommufd: Improve a few unclear bits of code
  iommufd: Fix comment typos
  vfio: Move vfio group specific code into group.c
  vfio: Refactor dma APIs for emulated devices
  vfio: Wrap vfio group module init/clean code into helpers
  vfio: Refactor vfio_device open and close
  vfio: Make vfio_device_open() truly device specific
  vfio: Swap order of vfio_device_container_register() and open_device()
  vfio: Set device->group in helper function
  vfio: Create wrappers for group register/unregister
  vfio: Move the sanity check of the group to vfio_create_group()
  vfio: Simplify vfio_create_group()
  iommufd: Allow iommufd to supply /dev/vfio/vfio
  vfio: Make vfio_container optionally compiled
  vfio: Move container related MODULE_ALIAS statements into container.c
  vfio-iommufd: Support iommufd for emulated VFIO devices
  vfio-iommufd: Support iommufd for physical VFIO devices
  vfio-iommufd: Allow iommufd to be used in place of a container fd
  vfio: Use IOMMU_CAP_ENFORCE_CACHE_COHERENCY for vfio_file_enforced_coherent()
  ...

1 files changed, 772 insertions, 0 deletions

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
new file mode 100644
index 000000000000..d81f93a321af
--- /dev/null
+++ b/drivers/iommu/iommufd/device.c
@@ -0,0 +1,772 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2021-2022, NVIDIA CORPORATION & AFFILIATES
+ */
+#include <linux/iommufd.h>
+#include <linux/slab.h>
+#include <linux/iommu.h>
+#include <linux/irqdomain.h>
+
+#include "io_pagetable.h"
+#include "iommufd_private.h"
+
+static bool allow_unsafe_interrupts;
+module_param(allow_unsafe_interrupts, bool, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(
+	allow_unsafe_interrupts,
+	"Allow IOMMUFD to bind to devices even if the platform cannot isolate "
+	"the MSI interrupt window. Enabling this is a security weakness.");
+
+/*
+ * A iommufd_device object represents the binding relationship between a
+ * consuming driver and the iommufd. These objects are created/destroyed by
+ * external drivers, not by userspace.
+ */
+struct iommufd_device {
+	struct iommufd_object obj;
+	struct iommufd_ctx *ictx;
+	struct iommufd_hw_pagetable *hwpt;
+	/* Head at iommufd_hw_pagetable::devices */
+	struct list_head devices_item;
+	/* always the physical device */
+	struct device *dev;
+	struct iommu_group *group;
+	bool enforce_cache_coherency;
+};
+
+void iommufd_device_destroy(struct iommufd_object *obj)
+{
+	struct iommufd_device *idev =
+		container_of(obj, struct iommufd_device, obj);
+
+	iommu_device_release_dma_owner(idev->dev);
+	iommu_group_put(idev->group);
+	iommufd_ctx_put(idev->ictx);
+}
+
+/**
+ * iommufd_device_bind - Bind a physical device to an iommu fd
+ * @ictx: iommufd file descriptor
+ * @dev: Pointer to a physical device struct
+ * @id: Output ID number to return to userspace for this device
+ *
+ * A successful bind establishes an ownership over the device and returns
+ * struct iommufd_device pointer, otherwise returns error pointer.
+ *
+ * A driver using this API must set driver_managed_dma and must not touch
+ * the device until this routine succeeds and establishes ownership.
+ *
+ * Binding a PCI device places the entire RID under iommufd control.
+ *
+ * The caller must undo this with iommufd_device_unbind()
+ */
+struct iommufd_device *iommufd_device_bind(struct iommufd_ctx *ictx,
+					   struct device *dev, u32 *id)
+{
+	struct iommufd_device *idev;
+	struct iommu_group *group;
+	int rc;
+
+	/*
+	 * iommufd always sets IOMMU_CACHE because we offer no way for userspace
+	 * to restore cache coherency.
+	 */
+	if (!device_iommu_capable(dev, IOMMU_CAP_CACHE_COHERENCY))
+		return ERR_PTR(-EINVAL);
+
+	group = iommu_group_get(dev);
+	if (!group)
+		return ERR_PTR(-ENODEV);
+
+	rc = iommu_device_claim_dma_owner(dev, ictx);
+	if (rc)
+		goto out_group_put;
+
+	idev = iommufd_object_alloc(ictx, idev, IOMMUFD_OBJ_DEVICE);
+	if (IS_ERR(idev)) {
+		rc = PTR_ERR(idev);
+		goto out_release_owner;
+	}
+	idev->ictx = ictx;
+	iommufd_ctx_get(ictx);
+	idev->dev = dev;
+	idev->enforce_cache_coherency =
+		device_iommu_capable(dev, IOMMU_CAP_ENFORCE_CACHE_COHERENCY);
+	/* The calling driver is a user until iommufd_device_unbind() */
+	refcount_inc(&idev->obj.users);
+	/* group refcount moves into iommufd_device */
+	idev->group = group;
+
+	/*
+	 * If the caller fails after this success it must call
+	 * iommufd_unbind_device() which is safe since we hold this refcount.
+	 * This also means the device is a leaf in the graph and no other object
+	 * can take a reference on it.
+	 */
+	iommufd_object_finalize(ictx, &idev->obj);
+	*id = idev->obj.id;
+	return idev;
+
+out_release_owner:
+	iommu_device_release_dma_owner(dev);
+out_group_put:
+	iommu_group_put(group);
+	return ERR_PTR(rc);
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_device_bind, IOMMUFD);
+
+/**
+ * iommufd_device_unbind - Undo iommufd_device_bind()
+ * @idev: Device returned by iommufd_device_bind()
+ *
+ * Release the device from iommufd control. The DMA ownership will return back
+ * to unowned with DMA controlled by the DMA API. This invalidates the
+ * iommufd_device pointer, other APIs that consume it must not be called
+ * concurrently.
+ */
+void iommufd_device_unbind(struct iommufd_device *idev)
+{
+	bool was_destroyed;
+
+	was_destroyed = iommufd_object_destroy_user(idev->ictx, &idev->obj);
+	WARN_ON(!was_destroyed);
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_device_unbind, IOMMUFD);
+
+static int iommufd_device_setup_msi(struct iommufd_device *idev,
+				    struct iommufd_hw_pagetable *hwpt,
+				    phys_addr_t sw_msi_start)
+{
+	int rc;
+
+	/*
+	 * If the IOMMU driver gives a IOMMU_RESV_SW_MSI then it is asking us to
+	 * call iommu_get_msi_cookie() on its behalf. This is necessary to setup
+	 * the MSI window so iommu_dma_prepare_msi() can install pages into our
+	 * domain after request_irq(). If it is not done interrupts will not
+	 * work on this domain.
+	 *
+	 * FIXME: This is conceptually broken for iommufd since we want to allow
+	 * userspace to change the domains, eg switch from an identity IOAS to a
+	 * DMA IOAS. There is currently no way to create a MSI window that
+	 * matches what the IRQ layer actually expects in a newly created
+	 * domain.
+	 */
+	if (sw_msi_start != PHYS_ADDR_MAX && !hwpt->msi_cookie) {
+		rc = iommu_get_msi_cookie(hwpt->domain, sw_msi_start);
+		if (rc)
+			return rc;
+
+		/*
+		 * iommu_get_msi_cookie() can only be called once per domain,
+		 * it returns -EBUSY on later calls.
+		 */
+		hwpt->msi_cookie = true;
+	}
+
+	/*
+	 * For historical compat with VFIO the insecure interrupt path is
+	 * allowed if the module parameter is set. Insecure means that a MemWr
+	 * operation from the device (eg a simple DMA) cannot trigger an
+	 * interrupt outside this iommufd context.
+	 */
+	if (!device_iommu_capable(idev->dev, IOMMU_CAP_INTR_REMAP) &&
+	    !irq_domain_check_msi_remap()) {
+		if (!allow_unsafe_interrupts)
+			return -EPERM;
+
+		dev_warn(
+			idev->dev,
+			"MSI interrupts are not secure, they cannot be isolated by the platform. "
+			"Check that platform features like interrupt remapping are enabled. "
+			"Use the \"allow_unsafe_interrupts\" module parameter to override\n");
+	}
+	return 0;
+}
+
+static bool iommufd_hw_pagetable_has_group(struct iommufd_hw_pagetable *hwpt,
+					   struct iommu_group *group)
+{
+	struct iommufd_device *cur_dev;
+
+	list_for_each_entry(cur_dev, &hwpt->devices, devices_item)
+		if (cur_dev->group == group)
+			return true;
+	return false;
+}
+
+static int iommufd_device_do_attach(struct iommufd_device *idev,
+				    struct iommufd_hw_pagetable *hwpt)
+{
+	phys_addr_t sw_msi_start = PHYS_ADDR_MAX;
+	int rc;
+
+	mutex_lock(&hwpt->devices_lock);
+
+	/*
+	 * Try to upgrade the domain we have, it is an iommu driver bug to
+	 * report IOMMU_CAP_ENFORCE_CACHE_COHERENCY but fail
+	 * enforce_cache_coherency when there are no devices attached to the
+	 * domain.
+	 */
+	if (idev->enforce_cache_coherency && !hwpt->enforce_cache_coherency) {
+		if (hwpt->domain->ops->enforce_cache_coherency)
+			hwpt->enforce_cache_coherency =
+				hwpt->domain->ops->enforce_cache_coherency(
+					hwpt->domain);
+		if (!hwpt->enforce_cache_coherency) {
+			WARN_ON(list_empty(&hwpt->devices));
+			rc = -EINVAL;
+			goto out_unlock;
+		}
+	}
+
+	rc = iopt_table_enforce_group_resv_regions(&hwpt->ioas->iopt, idev->dev,
+						   idev->group, &sw_msi_start);
+	if (rc)
+		goto out_unlock;
+
+	rc = iommufd_device_setup_msi(idev, hwpt, sw_msi_start);
+	if (rc)
+		goto out_iova;
+
+	/*
+	 * FIXME: Hack around missing a device-centric iommu api, only attach to
+	 * the group once for the first device that is in the group.
+	 */
+	if (!iommufd_hw_pagetable_has_group(hwpt, idev->group)) {
+		rc = iommu_attach_group(hwpt->domain, idev->group);
+		if (rc)
+			goto out_iova;
+
+		if (list_empty(&hwpt->devices)) {
+			rc = iopt_table_add_domain(&hwpt->ioas->iopt,
+						   hwpt->domain);
+			if (rc)
+				goto out_detach;
+		}
+	}
+
+	idev->hwpt = hwpt;
+	refcount_inc(&hwpt->obj.users);
+	list_add(&idev->devices_item, &hwpt->devices);
+	mutex_unlock(&hwpt->devices_lock);
+	return 0;
+
+out_detach:
+	iommu_detach_group(hwpt->domain, idev->group);
+out_iova:
+	iopt_remove_reserved_iova(&hwpt->ioas->iopt, idev->dev);
+out_unlock:
+	mutex_unlock(&hwpt->devices_lock);
+	return rc;
+}
+
+/*
+ * When automatically managing the domains we search for a compatible domain in
+ * the iopt and if one is found use it, otherwise create a new domain.
+ * Automatic domain selection will never pick a manually created domain.
+ */
+static int iommufd_device_auto_get_domain(struct iommufd_device *idev,
+					  struct iommufd_ioas *ioas)
+{
+	struct iommufd_hw_pagetable *hwpt;
+	int rc;
+
+	/*
+	 * There is no differentiation when domains are allocated, so any domain
+	 * that is willing to attach to the device is interchangeable with any
+	 * other.
+	 */
+	mutex_lock(&ioas->mutex);
+	list_for_each_entry(hwpt, &ioas->hwpt_list, hwpt_item) {
+		if (!hwpt->auto_domain)
+			continue;
+
+		rc = iommufd_device_do_attach(idev, hwpt);
+
+		/*
+		 * -EINVAL means the domain is incompatible with the device.
+		 * Other error codes should propagate to userspace as failure.
+		 * Success means the domain is attached.
+		 */
+		if (rc == -EINVAL)
+			continue;
+		goto out_unlock;
+	}
+
+	hwpt = iommufd_hw_pagetable_alloc(idev->ictx, ioas, idev->dev);
+	if (IS_ERR(hwpt)) {
+		rc = PTR_ERR(hwpt);
+		goto out_unlock;
+	}
+	hwpt->auto_domain = true;
+
+	rc = iommufd_device_do_attach(idev, hwpt);
+	if (rc)
+		goto out_abort;
+	list_add_tail(&hwpt->hwpt_item, &ioas->hwpt_list);
+
+	mutex_unlock(&ioas->mutex);
+	iommufd_object_finalize(idev->ictx, &hwpt->obj);
+	return 0;
+
+out_abort:
+	iommufd_object_abort_and_destroy(idev->ictx, &hwpt->obj);
+out_unlock:
+	mutex_unlock(&ioas->mutex);
+	return rc;
+}
+
+/**
+ * iommufd_device_attach - Connect a device from an iommu_domain
+ * @idev: device to attach
+ * @pt_id: Input a IOMMUFD_OBJ_IOAS, or IOMMUFD_OBJ_HW_PAGETABLE
+ *         Output the IOMMUFD_OBJ_HW_PAGETABLE ID
+ *
+ * This connects the device to an iommu_domain, either automatically or manually
+ * selected. Once this completes the device could do DMA.
+ *
+ * The caller should return the resulting pt_id back to userspace.
+ * This function is undone by calling iommufd_device_detach().
+ */
+int iommufd_device_attach(struct iommufd_device *idev, u32 *pt_id)
+{
+	struct iommufd_object *pt_obj;
+	int rc;
+
+	pt_obj = iommufd_get_object(idev->ictx, *pt_id, IOMMUFD_OBJ_ANY);
+	if (IS_ERR(pt_obj))
+		return PTR_ERR(pt_obj);
+
+	switch (pt_obj->type) {
+	case IOMMUFD_OBJ_HW_PAGETABLE: {
+		struct iommufd_hw_pagetable *hwpt =
+			container_of(pt_obj, struct iommufd_hw_pagetable, obj);
+
+		rc = iommufd_device_do_attach(idev, hwpt);
+		if (rc)
+			goto out_put_pt_obj;
+
+		mutex_lock(&hwpt->ioas->mutex);
+		list_add_tail(&hwpt->hwpt_item, &hwpt->ioas->hwpt_list);
+		mutex_unlock(&hwpt->ioas->mutex);
+		break;
+	}
+	case IOMMUFD_OBJ_IOAS: {
+		struct iommufd_ioas *ioas =
+			container_of(pt_obj, struct iommufd_ioas, obj);
+
+		rc = iommufd_device_auto_get_domain(idev, ioas);
+		if (rc)
+			goto out_put_pt_obj;
+		break;
+	}
+	default:
+		rc = -EINVAL;
+		goto out_put_pt_obj;
+	}
+
+	refcount_inc(&idev->obj.users);
+	*pt_id = idev->hwpt->obj.id;
+	rc = 0;
+
+out_put_pt_obj:
+	iommufd_put_object(pt_obj);
+	return rc;
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_device_attach, IOMMUFD);
+
+/**
+ * iommufd_device_detach - Disconnect a device to an iommu_domain
+ * @idev: device to detach
+ *
+ * Undo iommufd_device_attach(). This disconnects the idev from the previously
+ * attached pt_id. The device returns back to a blocked DMA translation.
+ */
+void iommufd_device_detach(struct iommufd_device *idev)
+{
+	struct iommufd_hw_pagetable *hwpt = idev->hwpt;
+
+	mutex_lock(&hwpt->ioas->mutex);
+	mutex_lock(&hwpt->devices_lock);
+	list_del(&idev->devices_item);
+	if (!iommufd_hw_pagetable_has_group(hwpt, idev->group)) {
+		if (list_empty(&hwpt->devices)) {
+			iopt_table_remove_domain(&hwpt->ioas->iopt,
+						 hwpt->domain);
+			list_del(&hwpt->hwpt_item);
+		}
+		iommu_detach_group(hwpt->domain, idev->group);
+	}
+	iopt_remove_reserved_iova(&hwpt->ioas->iopt, idev->dev);
+	mutex_unlock(&hwpt->devices_lock);
+	mutex_unlock(&hwpt->ioas->mutex);
+
+	if (hwpt->auto_domain)
+		iommufd_object_destroy_user(idev->ictx, &hwpt->obj);
+	else
+		refcount_dec(&hwpt->obj.users);
+
+	idev->hwpt = NULL;
+
+	refcount_dec(&idev->obj.users);
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_device_detach, IOMMUFD);
+
+void iommufd_access_destroy_object(struct iommufd_object *obj)
+{
+	struct iommufd_access *access =
+		container_of(obj, struct iommufd_access, obj);
+
+	iopt_remove_access(&access->ioas->iopt, access);
+	iommufd_ctx_put(access->ictx);
+	refcount_dec(&access->ioas->obj.users);
+}
+
+/**
+ * iommufd_access_create - Create an iommufd_access
+ * @ictx: iommufd file descriptor
+ * @ioas_id: ID for a IOMMUFD_OBJ_IOAS
+ * @ops: Driver's ops to associate with the access
+ * @data: Opaque data to pass into ops functions
+ *
+ * An iommufd_access allows a driver to read/write to the IOAS without using
+ * DMA. The underlying CPU memory can be accessed using the
+ * iommufd_access_pin_pages() or iommufd_access_rw() functions.
+ *
+ * The provided ops are required to use iommufd_access_pin_pages().
+ */
+struct iommufd_access *
+iommufd_access_create(struct iommufd_ctx *ictx, u32 ioas_id,
+		      const struct iommufd_access_ops *ops, void *data)
+{
+	struct iommufd_access *access;
+	struct iommufd_object *obj;
+	int rc;
+
+	/*
+	 * There is no uAPI for the access object, but to keep things symmetric
+	 * use the object infrastructure anyhow.
+	 */
+	access = iommufd_object_alloc(ictx, access, IOMMUFD_OBJ_ACCESS);
+	if (IS_ERR(access))
+		return access;
+
+	access->data = data;
+	access->ops = ops;
+
+	obj = iommufd_get_object(ictx, ioas_id, IOMMUFD_OBJ_IOAS);
+	if (IS_ERR(obj)) {
+		rc = PTR_ERR(obj);
+		goto out_abort;
+	}
+	access->ioas = container_of(obj, struct iommufd_ioas, obj);
+	iommufd_ref_to_users(obj);
+
+	if (ops->needs_pin_pages)
+		access->iova_alignment = PAGE_SIZE;
+	else
+		access->iova_alignment = 1;
+	rc = iopt_add_access(&access->ioas->iopt, access);
+	if (rc)
+		goto out_put_ioas;
+
+	/* The calling driver is a user until iommufd_access_destroy() */
+	refcount_inc(&access->obj.users);
+	access->ictx = ictx;
+	iommufd_ctx_get(ictx);
+	iommufd_object_finalize(ictx, &access->obj);
+	return access;
+out_put_ioas:
+	refcount_dec(&access->ioas->obj.users);
+out_abort:
+	iommufd_object_abort(ictx, &access->obj);
+	return ERR_PTR(rc);
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_access_create, IOMMUFD);
+
+/**
+ * iommufd_access_destroy - Destroy an iommufd_access
+ * @access: The access to destroy
+ *
+ * The caller must stop using the access before destroying it.
+ */
+void iommufd_access_destroy(struct iommufd_access *access)
+{
+	bool was_destroyed;
+
+	was_destroyed = iommufd_object_destroy_user(access->ictx, &access->obj);
+	WARN_ON(!was_destroyed);
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_access_destroy, IOMMUFD);
+
+/**
+ * iommufd_access_notify_unmap - Notify users of an iopt to stop using it
+ * @iopt: iopt to work on
+ * @iova: Starting iova in the iopt
+ * @length: Number of bytes
+ *
+ * After this function returns there should be no users attached to the pages
+ * linked to this iopt that intersect with iova,length. Anyone that has attached
+ * a user through iopt_access_pages() needs to detach it through
+ * iommufd_access_unpin_pages() before this function returns.
+ *
+ * iommufd_access_destroy() will wait for any outstanding unmap callback to
+ * complete. Once iommufd_access_destroy() no unmap ops are running or will
+ * run in the future. Due to this a driver must not create locking that prevents
+ * unmap to complete while iommufd_access_destroy() is running.
+ */
+void iommufd_access_notify_unmap(struct io_pagetable *iopt, unsigned long iova,
+				 unsigned long length)
+{
+	struct iommufd_ioas *ioas =
+		container_of(iopt, struct iommufd_ioas, iopt);
+	struct iommufd_access *access;
+	unsigned long index;
+
+	xa_lock(&ioas->iopt.access_list);
+	xa_for_each(&ioas->iopt.access_list, index, access) {
+		if (!iommufd_lock_obj(&access->obj))
+			continue;
+		xa_unlock(&ioas->iopt.access_list);
+
+		access->ops->unmap(access->data, iova, length);
+
+		iommufd_put_object(&access->obj);
+		xa_lock(&ioas->iopt.access_list);
+	}
+	xa_unlock(&ioas->iopt.access_list);
+}
+
+/**
+ * iommufd_access_unpin_pages() - Undo iommufd_access_pin_pages
+ * @access: IOAS access to act on
+ * @iova: Starting IOVA
+ * @length: Number of bytes to access
+ *
+ * Return the struct page's. The caller must stop accessing them before calling
+ * this. The iova/length must exactly match the one provided to access_pages.
+ */
+void iommufd_access_unpin_pages(struct iommufd_access *access,
+				unsigned long iova, unsigned long length)
+{
+	struct io_pagetable *iopt = &access->ioas->iopt;
+	struct iopt_area_contig_iter iter;
+	unsigned long last_iova;
+	struct iopt_area *area;
+
+	if (WARN_ON(!length) ||
+	    WARN_ON(check_add_overflow(iova, length - 1, &last_iova)))
+		return;
+
+	down_read(&iopt->iova_rwsem);
+	iopt_for_each_contig_area(&iter, area, iopt, iova, last_iova)
+		iopt_area_remove_access(
+			area, iopt_area_iova_to_index(area, iter.cur_iova),
+			iopt_area_iova_to_index(
+				area,
+				min(last_iova, iopt_area_last_iova(area))));
+	up_read(&iopt->iova_rwsem);
+	WARN_ON(!iopt_area_contig_done(&iter));
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_access_unpin_pages, IOMMUFD);
+
+static bool iopt_area_contig_is_aligned(struct iopt_area_contig_iter *iter)
+{
+	if (iopt_area_start_byte(iter->area, iter->cur_iova) % PAGE_SIZE)
+		return false;
+
+	if (!iopt_area_contig_done(iter) &&
+	    (iopt_area_start_byte(iter->area, iopt_area_last_iova(iter->area)) %
+	     PAGE_SIZE) != (PAGE_SIZE - 1))
+		return false;
+	return true;
+}
+
+static bool check_area_prot(struct iopt_area *area, unsigned int flags)
+{
+	if (flags & IOMMUFD_ACCESS_RW_WRITE)
+		return area->iommu_prot & IOMMU_WRITE;
+	return area->iommu_prot & IOMMU_READ;
+}
+
+/**
+ * iommufd_access_pin_pages() - Return a list of pages under the iova
+ * @access: IOAS access to act on
+ * @iova: Starting IOVA
+ * @length: Number of bytes to access
+ * @out_pages: Output page list
+ * @flags: IOPMMUFD_ACCESS_RW_* flags
+ *
+ * Reads @length bytes starting at iova and returns the struct page * pointers.
+ * These can be kmap'd by the caller for CPU access.
+ *
+ * The caller must perform iommufd_access_unpin_pages() when done to balance
+ * this.
+ *
+ * This API always requires a page aligned iova. This happens naturally if the
+ * ioas alignment is >= PAGE_SIZE and the iova is PAGE_SIZE aligned. However
+ * smaller alignments have corner cases where this API can fail on otherwise
+ * aligned iova.
+ */
+int iommufd_access_pin_pages(struct iommufd_access *access, unsigned long iova,
+			     unsigned long length, struct page **out_pages,
+			     unsigned int flags)
+{
+	struct io_pagetable *iopt = &access->ioas->iopt;
+	struct iopt_area_contig_iter iter;
+	unsigned long last_iova;
+	struct iopt_area *area;
+	int rc;
+
+	/* Driver's ops don't support pin_pages */
+	if (IS_ENABLED(CONFIG_IOMMUFD_TEST) &&
+	    WARN_ON(access->iova_alignment != PAGE_SIZE || !access->ops->unmap))
+		return -EINVAL;
+
+	if (!length)
+		return -EINVAL;
+	if (check_add_overflow(iova, length - 1, &last_iova))
+		return -EOVERFLOW;
+
+	down_read(&iopt->iova_rwsem);
+	iopt_for_each_contig_area(&iter, area, iopt, iova, last_iova) {
+		unsigned long last = min(last_iova, iopt_area_last_iova(area));
+		unsigned long last_index = iopt_area_iova_to_index(area, last);
+		unsigned long index =
+			iopt_area_iova_to_index(area, iter.cur_iova);
+
+		if (area->prevent_access ||
+		    !iopt_area_contig_is_aligned(&iter)) {
+			rc = -EINVAL;
+			goto err_remove;
+		}
+
+		if (!check_area_prot(area, flags)) {
+			rc = -EPERM;
+			goto err_remove;
+		}
+
+		rc = iopt_area_add_access(area, index, last_index, out_pages,
+					  flags);
+		if (rc)
+			goto err_remove;
+		out_pages += last_index - index + 1;
+	}
+	if (!iopt_area_contig_done(&iter)) {
+		rc = -ENOENT;
+		goto err_remove;
+	}
+
+	up_read(&iopt->iova_rwsem);
+	return 0;
+
+err_remove:
+	if (iova < iter.cur_iova) {
+		last_iova = iter.cur_iova - 1;
+		iopt_for_each_contig_area(&iter, area, iopt, iova, last_iova)
+			iopt_area_remove_access(
+				area,
+				iopt_area_iova_to_index(area, iter.cur_iova),
+				iopt_area_iova_to_index(
+					area, min(last_iova,
+						  iopt_area_last_iova(area))));
+	}
+	up_read(&iopt->iova_rwsem);
+	return rc;
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_access_pin_pages, IOMMUFD);
+
+/**
+ * iommufd_access_rw - Read or write data under the iova
+ * @access: IOAS access to act on
+ * @iova: Starting IOVA
+ * @data: Kernel buffer to copy to/from
+ * @length: Number of bytes to access
+ * @flags: IOMMUFD_ACCESS_RW_* flags
+ *
+ * Copy kernel to/from data into the range given by IOVA/length. If flags
+ * indicates IOMMUFD_ACCESS_RW_KTHREAD then a large copy can be optimized
+ * by changing it into copy_to/from_user().
+ */
+int iommufd_access_rw(struct iommufd_access *access, unsigned long iova,
+		      void *data, size_t length, unsigned int flags)
+{
+	struct io_pagetable *iopt = &access->ioas->iopt;
+	struct iopt_area_contig_iter iter;
+	struct iopt_area *area;
+	unsigned long last_iova;
+	int rc;
+
+	if (!length)
+		return -EINVAL;
+	if (check_add_overflow(iova, length - 1, &last_iova))
+		return -EOVERFLOW;
+
+	down_read(&iopt->iova_rwsem);
+	iopt_for_each_contig_area(&iter, area, iopt, iova, last_iova) {
+		unsigned long last = min(last_iova, iopt_area_last_iova(area));
+		unsigned long bytes = (last - iter.cur_iova) + 1;
+
+		if (area->prevent_access) {
+			rc = -EINVAL;
+			goto err_out;
+		}
+
+		if (!check_area_prot(area, flags)) {
+			rc = -EPERM;
+			goto err_out;
+		}
+
+		rc = iopt_pages_rw_access(
+			area->pages, iopt_area_start_byte(area, iter.cur_iova),
+			data, bytes, flags);
+		if (rc)
+			goto err_out;
+		data += bytes;
+	}
+	if (!iopt_area_contig_done(&iter))
+		rc = -ENOENT;
+err_out:
+	up_read(&iopt->iova_rwsem);
+	return rc;
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_access_rw, IOMMUFD);
+
+#ifdef CONFIG_IOMMUFD_TEST
+/*
+ * Creating a real iommufd_device is too hard, bypass creating a iommufd_device
+ * and go directly to attaching a domain.
+ */
+struct iommufd_hw_pagetable *
+iommufd_device_selftest_attach(struct iommufd_ctx *ictx,
+			       struct iommufd_ioas *ioas,
+			       struct device *mock_dev)
+{
+	struct iommufd_hw_pagetable *hwpt;
+	int rc;
+
+	hwpt = iommufd_hw_pagetable_alloc(ictx, ioas, mock_dev);
+	if (IS_ERR(hwpt))
+		return hwpt;
+
+	rc = iopt_table_add_domain(&hwpt->ioas->iopt, hwpt->domain);
+	if (rc)
+		goto out_hwpt;
+
+	refcount_inc(&hwpt->obj.users);
+	iommufd_object_finalize(ictx, &hwpt->obj);
+	return hwpt;
+
+out_hwpt:
+	iommufd_object_abort_and_destroy(ictx, &hwpt->obj);
+	return ERR_PTR(rc);
+}
+
+void iommufd_device_selftest_detach(struct iommufd_ctx *ictx,
+				    struct iommufd_hw_pagetable *hwpt)
+{
+	iopt_table_remove_domain(&hwpt->ioas->iopt, hwpt->domain);
+	refcount_dec(&hwpt->obj.users);
+}
+#endif