[PATCH RFC v2 10/13] iommufd: Add kAPI toward external drivers for physical devices

Jason Gunthorpe
2022-09-02T19:59:52Z

Add the four functions external drivers need to connect physical DMA to
the IOMMUFD:

iommufd_device_bind() / iommufd_device_unbind()
Register the device with iommufd and establish security isolation.

iommufd_device_attach() / iommufd_device_detach()
Connect a bound device to a page table

Binding a device creates a device object ID in the uAPI, however the
generic API provides no IOCTLs to manipulate them.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
drivers/iommu/iommufd/Makefile | 1 +
drivers/iommu/iommufd/device.c | 396 ++++++++++++++++++++++++
drivers/iommu/iommufd/iommufd_private.h | 4 +
drivers/iommu/iommufd/main.c | 3 +
include/linux/iommufd.h | 14 +
5 files changed, 418 insertions(+)
create mode 100644 drivers/iommu/iommufd/device.c

diff --git a/drivers/iommu/iommufd/Makefile b/drivers/iommu/iommufd/Makefile
index e13e971aa28c60..ca28a135b9675f 100644
--- a/drivers/iommu/iommufd/Makefile
+++ b/drivers/iommu/iommufd/Makefile
@@ -1,5 +1,6 @@
# SPDX-License-Identifier: GPL-2.0-only
iommufd-y := \
+ device.o \
hw_pagetable.o \
io_pagetable.o \
ioas.o \
diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
new file mode 100644
index 00000000000000..23b101db846f40
--- /dev/null
+++ b/drivers/iommu/iommufd/device.c
@@ -0,0 +1,396 @@
+// 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/file.h>
+#include <linux/pci.h>
+#include <linux/irqdomain.h>
+#include <linux/dma-iommu.h>
+#include <linux/dma-map-ops.h>
+
+#include "iommufd_private.h"
+
+/*
+ * 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;
+};
+
+void iommufd_device_destroy(struct iommufd_object *obj)
+{
+ struct iommufd_device *idev =
+ container_of(obj, struct iommufd_device, obj);
+
+ iommu_group_release_dma_owner(idev->group);
+ 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 PCI 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_unbind_device()
+ */
+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 (!iommu_capable(dev->bus, IOMMU_CAP_CACHE_COHERENCY))
+ return ERR_PTR(-EINVAL);
+
+ group = iommu_group_get(dev);
+ if (!group)
+ return ERR_PTR(-ENODEV);
+
+ /*
+ * FIXME: Use a device-centric iommu api, this won't work with
+ * multi-device groups
+ */
+ rc = iommu_group_claim_dma_owner(group, 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;
+ /* 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_group_release_dma_owner(group);
+out_group_put:
+ iommu_group_put(group);
+ return ERR_PTR(rc);
+}
+EXPORT_SYMBOL_GPL(iommufd_device_bind);
+
+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_GPL(iommufd_device_unbind);
+
+/**
+ * iommufd_device_enforced_coherent - True if no-snoop TLPs are blocked
+ * @idev: device to query
+ *
+ * This can only be called if the device is attached, and the caller must ensure
+ * that the this is not raced with iommufd_device_attach() /
+ * iommufd_device_detach().
+ */
+bool iommufd_device_enforced_coherent(struct iommufd_device *idev)
+{
+ return iommufd_ioas_enforced_coherent(idev->hwpt->ioas);
+}
+EXPORT_SYMBOL_GPL(iommufd_device_enforced_coherent);
+
+static int iommufd_device_setup_msi(struct iommufd_device *idev,
+ struct iommufd_hw_pagetable *hwpt,
+ phys_addr_t sw_msi_start,
+ unsigned int flags)
+{
+ int rc;
+
+ /*
+ * IOMMU_CAP_INTR_REMAP means that the platform is isolating MSI,
+ * nothing further to do.
+ */
+ if (iommu_capable(idev->dev->bus, IOMMU_CAP_INTR_REMAP))
+ return 0;
+
+ /*
+ * On ARM systems that set the global IRQ_DOMAIN_FLAG_MSI_REMAP every
+ * allocated iommu_domain will block interrupts by default and this
+ * special flow is needed to turn them back on.
+ */
+ if (irq_domain_check_msi_remap()) {
+ if (WARN_ON(!sw_msi_start))
+ return -EPERM;
+ /*
+ * iommu_get_msi_cookie() can only be called once per domain,
+ * it returns -EBUSY on later calls.
+ */
+ if (hwpt->msi_cookie)
+ return 0;
+ rc = iommu_get_msi_cookie(hwpt->domain, sw_msi_start);
+ if (rc && rc != -ENODEV)
+ return rc;
+ hwpt->msi_cookie = true;
+ return 0;
+ }
+
+ /*
+ * Otherwise the platform has a MSI window that is not isolated. For
+ * historical compat with VFIO allow a module parameter to ignore the
+ * insecurity.
+ */
+ if (!(flags & IOMMUFD_ATTACH_FLAGS_ALLOW_UNSAFE_INTERRUPT))
+ return -EPERM;
+ 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,
+ unsigned int flags)
+{
+ int rc;
+
+ mutex_lock(&hwpt->devices_lock);
+ /*
+ * FIXME: Use a device-centric iommu api. For now check if the
+ * hw_pagetable already has a device of the same group joined to tell if
+ * we are the first and need to attach the group.
+ */
+ if (!iommufd_hw_pagetable_has_group(hwpt, idev->group)) {
+ phys_addr_t sw_msi_start = 0;
+
+ rc = iommu_attach_group(hwpt->domain, idev->group);
+ if (rc)
+ goto out_unlock;
+
+ /*
+ * hwpt is now the exclusive owner of the group so this is the
+ * first time enforce is called for this group.
+ */
+ rc = iopt_table_enforce_group_resv_regions(
+ &hwpt->ioas->iopt, idev->group, &sw_msi_start);
+ if (rc)
+ goto out_detach;
+ rc = iommufd_device_setup_msi(idev, hwpt, sw_msi_start, flags);
+ if (rc)
+ goto out_iova;
+
+ if (list_empty(&hwpt->devices)) {
+ rc = iopt_table_add_domain(&hwpt->ioas->iopt,
+ hwpt->domain);
+ if (rc)
+ goto out_iova;
+ }
+ }
+
+ idev->hwpt = hwpt;
+ refcount_inc(&hwpt->obj.users);
+ list_add(&idev->devices_item, &hwpt->devices);
+ mutex_unlock(&hwpt->devices_lock);
+ return 0;
+
+out_iova:
+ iopt_remove_reserved_iova(&hwpt->ioas->iopt, idev->group);
+out_detach:
+ iommu_detach_group(hwpt->domain, idev->group);
+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,
+ unsigned int flags)
+{
+ 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 ||
+ !refcount_inc_not_zero(&hwpt->obj.users))
+ continue;
+
+ /*
+ * FIXME: if the group is already attached to a domain make sure
+ * this returns EMEDIUMTYPE
+ */
+ rc = iommufd_device_do_attach(idev, hwpt, flags);
+ refcount_dec(&hwpt->obj.users);
+ if (rc) {
+ if (rc == -EMEDIUMTYPE)
+ continue;
+ goto out_unlock;
+ }
+ 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, flags);
+ 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 to 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
+ * @flags: Optional flags
+ *
+ * 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,
+ unsigned int flags)
+{
+ 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, flags);
+ 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, flags);
+ 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_GPL(iommufd_device_attach);
+
+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);
+ }
+ iopt_remove_reserved_iova(&hwpt->ioas->iopt, idev->group);
+ iommu_detach_group(hwpt->domain, idev->group);
+ }
+ 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_GPL(iommufd_device_detach);
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index 4f628800bc2b71..0ede92b0aa32b4 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -92,6 +92,7 @@ static inline int iommufd_ucmd_respond(struct iommufd_ucmd *ucmd,
enum iommufd_object_type {
IOMMUFD_OBJ_NONE,
IOMMUFD_OBJ_ANY = IOMMUFD_OBJ_NONE,
+ IOMMUFD_OBJ_DEVICE,
IOMMUFD_OBJ_HW_PAGETABLE,
IOMMUFD_OBJ_IOAS,
};
@@ -216,6 +217,7 @@ struct iommufd_hw_pagetable {
struct iommu_domain *domain;
bool auto_domain : 1;
bool enforce_cache_coherency : 1;
+ bool msi_cookie : 1;
/* Head at iommufd_ioas::hwpt_list */
struct list_head hwpt_item;
struct mutex devices_lock;
@@ -227,4 +229,6 @@ iommufd_hw_pagetable_alloc(struct iommufd_ctx *ictx, struct iommufd_ioas *ioas,
struct device *dev);
void iommufd_hw_pagetable_destroy(struct iommufd_object *obj);

+void iommufd_device_destroy(struct iommufd_object *obj);
+
#endif
diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index 2a9b581cacffb6..b09dbfc8009dc2 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -327,6 +327,9 @@ void iommufd_ctx_put(struct iommufd_ctx *ictx)
EXPORT_SYMBOL_GPL(iommufd_ctx_put);

static struct iommufd_object_ops iommufd_object_ops[] = {
+ [IOMMUFD_OBJ_DEVICE] = {
+ .destroy = iommufd_device_destroy,
+ },
[IOMMUFD_OBJ_IOAS] = {
.destroy = iommufd_ioas_destroy,
},
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index 9c6ec4d66b4a92..477c3ea098f637 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -9,12 +9,26 @@
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/err.h>
+#include <linux/device.h>

struct page;
+struct iommufd_device;
struct iommufd_ctx;
struct io_pagetable;
struct file;

+struct iommufd_device *iommufd_device_bind(struct iommufd_ctx *ictx,
+ struct device *dev, u32 *id);
+void iommufd_device_unbind(struct iommufd_device *idev);
+bool iommufd_device_enforced_coherent(struct iommufd_device *idev);
+
+enum {
+ IOMMUFD_ATTACH_FLAGS_ALLOW_UNSAFE_INTERRUPT = 1 << 0,
+};
+int iommufd_device_attach(struct iommufd_device *idev, u32 *pt_id,
+ unsigned int flags);
+void iommufd_device_detach(struct iommufd_device *idev);
+
int iopt_access_pages(struct io_pagetable *iopt, unsigned long iova,
unsigned long length, struct page **out_pages,
bool write);
--
2.37.3