[PATCH RFC 10/12] iommufd: Add kAPI toward external drivers

[Jason Gunthorpe <jgg@nvidia.com>]

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

iommufd_bind_pci_device() / iommufd_unbind_device()
  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.

An API to support the VFIO mdevs is a WIP at this point, but likely
involves requesting a struct iommufd_device without providing any struct
device, and then using the pin/unpin/rw operations on that iommufd_device.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/iommu/iommufd/Makefile          |   1 +
 drivers/iommu/iommufd/device.c          | 274 ++++++++++++++++++++++++
 drivers/iommu/iommufd/iommufd_private.h |   4 +
 drivers/iommu/iommufd/main.c            |   3 +
 include/linux/iommufd.h                 |  50 +++++
 5 files changed, 332 insertions(+)
 create mode 100644 drivers/iommu/iommufd/device.c
 create mode 100644 include/linux/iommufd.h

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..c20bc9eab07e13
--- /dev/null
+++ b/drivers/iommu/iommufd/device.c
@@ -0,0 +1,274 @@
+// 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 "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);
+	fput(idev->ictx->filp);
+}
+
+/**
+ * iommufd_bind_pci_device - Bind a physical device to an iommu fd
+ * @fd: iommufd file descriptor.
+ * @pdev: 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_bind_pci_device(int fd, struct pci_dev *pdev,
+					       u32 *id)
+{
+	struct iommufd_device *idev;
+	struct iommufd_ctx *ictx;
+	struct iommu_group *group;
+	int rc;
+
+	ictx = iommufd_fget(fd);
+	if (!ictx)
+		return ERR_PTR(-EINVAL);
+
+	group = iommu_group_get(&pdev->dev);
+	if (!group) {
+		rc = -ENODEV;
+		goto out_file_put;
+	}
+
+	/*
+	 * FIXME: Use a device-centric iommu api and this won't work with
+	 * multi-device groups
+	 */
+	rc = iommu_group_claim_dma_owner(group, ictx->filp);
+	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;
+	idev->dev = &pdev->dev;
+	/* The calling driver is a user until iommufd_unbind_device() */
+	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);
+out_file_put:
+	fput(ictx->filp);
+	return ERR_PTR(rc);
+}
+EXPORT_SYMBOL_GPL(iommufd_bind_pci_device);
+
+void iommufd_unbind_device(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_unbind_device);
+
+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_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;
+}
+
+/**
+ * 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_hw_pagetable *hwpt;
+	int rc;
+
+	refcount_inc(&idev->obj.users);
+
+	hwpt = iommufd_hw_pagetable_from_id(idev->ictx, *pt_id, idev->dev);
+	if (IS_ERR(hwpt)) {
+		rc = PTR_ERR(hwpt);
+		goto out_users;
+	}
+
+	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;
+	}
+
+	idev->hwpt = hwpt;
+	if (list_empty(&hwpt->devices)) {
+		rc = iopt_table_add_domain(&hwpt->ioas->iopt, hwpt->domain);
+		if (rc)
+			goto out_iova;
+	}
+	list_add(&idev->devices_item, &hwpt->devices);
+	mutex_unlock(&hwpt->devices_lock);
+
+	*pt_id = idev->hwpt->obj.id;
+	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);
+	iommufd_hw_pagetable_put(idev->ictx, hwpt);
+out_users:
+	refcount_dec(&idev->obj.users);
+	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->devices_lock);
+	list_del(&idev->devices_item);
+	if (!iommufd_hw_pagetable_has_group(hwpt, idev->group)) {
+		iopt_remove_reserved_iova(&hwpt->ioas->iopt, idev->group);
+		iommu_detach_group(hwpt->domain, idev->group);
+	}
+	if (list_empty(&hwpt->devices))
+		iopt_table_remove_domain(&hwpt->ioas->iopt, hwpt->domain);
+	mutex_unlock(&hwpt->devices_lock);
+
+	iommufd_hw_pagetable_put(idev->ictx, hwpt);
+	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 c5c9650cc86818..e5c717231f851e 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -96,6 +96,7 @@ 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,
 	IOMMUFD_OBJ_MAX,
@@ -196,6 +197,7 @@ struct iommufd_hw_pagetable {
 	struct iommufd_object obj;
 	struct iommufd_ioas *ioas;
 	struct iommu_domain *domain;
+	bool msi_cookie;
 	/* Head at iommufd_ioas::auto_domains */
 	struct list_head auto_domains_item;
 	struct mutex devices_lock;
@@ -209,4 +211,6 @@ void iommufd_hw_pagetable_put(struct iommufd_ctx *ictx,
 			      struct iommufd_hw_pagetable *hwpt);
 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 954cde173c86fc..6a895489fb5b82 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -284,6 +284,9 @@ struct iommufd_ctx *iommufd_fget(int fd)
 }
 
 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
new file mode 100644
index 00000000000000..6caac05475e39f
--- /dev/null
+++ b/include/linux/iommufd.h
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 Intel Corporation
+ * Copyright (c) 2021-2022, NVIDIA CORPORATION & AFFILIATES
+ */
+#ifndef __LINUX_IOMMUFD_H
+#define __LINUX_IOMMUFD_H
+
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/device.h>
+
+struct pci_dev;
+struct iommufd_device;
+
+#if IS_ENABLED(CONFIG_IOMMUFD)
+struct iommufd_device *iommufd_bind_pci_device(int fd, struct pci_dev *pdev,
+					       u32 *id);
+void iommufd_unbind_device(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);
+
+#else /* !CONFIG_IOMMUFD */
+static inline struct iommufd_device *
+iommufd_bind_pci_device(int fd, struct pci_dev *pdev, u32 *id)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+
+static inline void iommufd_unbind_device(struct iommufd_device *idev)
+{
+}
+
+static inline int iommufd_device_attach(struct iommufd_device *idev,
+					u32 ioas_id)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline void iommufd_device_detach(struct iommufd_device *idev)
+{
+}
+#endif /* CONFIG_IOMMUFD */
+#endif
-- 
2.35.1