[RFC PATCHES 08/17] iommufd: IO page fault delivery initialization and release

[Lu Baolu]

Add some housekeeping code for IO page fault dilivery. Add a fault field
in the iommufd_hw_pagetable structure to store pending IO page faults and
other related data.

The fault field is allocated when an IOPF-capable user HWPT (indicated by
IOMMU_HWPT_ALLOC_FLAGS_IOPF_CAPABLE being set in the allocation user data)
is allocated. This field exists until the HWPT is destroyed. This also
implies that it is possible to determine whether a HWPT is IOPF capable by
checking the fault field.

When an IOPF-capable HWPT is attached to a device (could also be a PASID of
a device in the future), a fault cookie is allocated and set to the device.
The cookie is cleared and freed when HWPT is detached from the device.

Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 drivers/iommu/iommufd/iommufd_private.h | 12 +++++
 drivers/iommu/iommufd/device.c          | 61 +++++++++++++++++++++++--
 drivers/iommu/iommufd/hw_pagetable.c    | 55 ++++++++++++++++++++++
 3 files changed, 125 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index e951815f5707..5ff139acc5c0 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -236,6 +236,13 @@ int iommufd_option_rlimit_mode(struct iommu_option *cmd,
 
 int iommufd_vfio_ioas(struct iommufd_ucmd *ucmd);
 
+struct hw_pgtable_fault {
+	struct mutex mutex;
+	struct list_head deliver;
+	struct list_head response;
+	struct eventfd_ctx *trigger;
+};
+
 /*
  * A HW pagetable is called an iommu_domain inside the kernel. This user object
  * allows directly creating and inspecting the domains. Domains that have kernel
@@ -252,6 +259,7 @@ struct iommufd_hw_pagetable {
 	bool msi_cookie : 1;
 	/* Head at iommufd_ioas::hwpt_list */
 	struct list_head hwpt_item;
+	struct hw_pgtable_fault *fault;
 };
 
 struct iommufd_hw_pagetable *
@@ -314,6 +322,10 @@ struct iommufd_device {
 	bool has_user_data;
 };
 
+struct iommufd_fault_cookie {
+	struct iommufd_device *idev;
+};
+
 static inline struct iommufd_device *
 iommufd_get_device(struct iommufd_ucmd *ucmd, u32 id)
 {
diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index 29b212714e2c..3408f1fc3e9f 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -374,6 +374,44 @@ static int iommufd_group_setup_msi(struct iommufd_group *igroup,
 	return 0;
 }
 
+static int iommufd_device_set_fault_cookie(struct iommufd_hw_pagetable *hwpt,
+					   struct iommufd_device *idev,
+					   ioasid_t pasid)
+{
+	struct iommufd_fault_cookie *fcookie, *curr;
+
+	if (!hwpt->fault)
+		return 0;
+
+	fcookie = kzalloc(sizeof(*fcookie), GFP_KERNEL);
+	if (!fcookie)
+		return -ENOMEM;
+	fcookie->idev = idev;
+
+	curr = iommu_set_device_fault_cookie(idev->dev, pasid, fcookie);
+	if (IS_ERR(curr)) {
+		kfree(fcookie);
+		return PTR_ERR(curr);
+	}
+	kfree(curr);
+
+	return 0;
+}
+
+static void iommufd_device_unset_fault_cookie(struct iommufd_hw_pagetable *hwpt,
+					      struct iommufd_device *idev,
+					      ioasid_t pasid)
+{
+	struct iommufd_fault_cookie *curr;
+
+	if (!hwpt->fault)
+		return;
+
+	curr = iommu_set_device_fault_cookie(idev->dev, pasid, NULL);
+	WARN_ON(IS_ERR(curr));
+	kfree(curr);
+}
+
 int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
 				struct iommufd_device *idev)
 {
@@ -398,6 +436,10 @@ int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
 	if (rc)
 		goto err_unlock;
 
+	rc = iommufd_device_set_fault_cookie(hwpt, idev, 0);
+	if (rc)
+		goto err_unresv;
+
 	/*
 	 * Only attach to the group once for the first device that is in the
 	 * group. All the other devices will follow this attachment. The user
@@ -408,17 +450,21 @@ int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
 	if (list_empty(&idev->igroup->device_list)) {
 		rc = iommufd_group_setup_msi(idev->igroup, hwpt);
 		if (rc)
-			goto err_unresv;
+			goto err_unset;
 
 		rc = iommu_attach_group(hwpt->domain, idev->igroup->group);
 		if (rc)
-			goto err_unresv;
+			goto err_unset;
 		idev->igroup->hwpt = hwpt;
 	}
+
 	refcount_inc(&hwpt->obj.users);
 	list_add_tail(&idev->group_item, &idev->igroup->device_list);
 	mutex_unlock(&idev->igroup->lock);
 	return 0;
+
+err_unset:
+	iommufd_device_unset_fault_cookie(hwpt, idev, 0);
 err_unresv:
 	iopt_remove_reserved_iova(&hwpt->ioas->iopt, idev->dev);
 err_unlock:
@@ -433,6 +479,7 @@ iommufd_hw_pagetable_detach(struct iommufd_device *idev)
 
 	mutex_lock(&idev->igroup->lock);
 	list_del(&idev->group_item);
+	iommufd_device_unset_fault_cookie(hwpt, idev, 0);
 	if (list_empty(&idev->igroup->device_list)) {
 		iommu_detach_group(hwpt->domain, idev->igroup->group);
 		idev->igroup->hwpt = NULL;
@@ -502,9 +549,14 @@ iommufd_device_do_replace(struct iommufd_device *idev,
 	if (rc)
 		goto err_unresv;
 
+	iommufd_device_unset_fault_cookie(old_hwpt, idev, 0);
+	rc = iommufd_device_set_fault_cookie(hwpt, idev, 0);
+	if (rc)
+		goto err_unresv;
+
 	rc = iommu_group_replace_domain(igroup->group, hwpt->domain);
 	if (rc)
-		goto err_unresv;
+		goto err_replace;
 
 	if (hwpt->ioas != old_hwpt->ioas) {
 		list_for_each_entry(cur, &igroup->device_list, group_item)
@@ -526,6 +578,9 @@ iommufd_device_do_replace(struct iommufd_device *idev,
 
 	/* Caller must destroy old_hwpt */
 	return old_hwpt;
+err_replace:
+	iommufd_device_unset_fault_cookie(hwpt, idev, 0);
+	iommufd_device_set_fault_cookie(old_hwpt, idev, 0);
 err_unresv:
 	list_for_each_entry(cur, &igroup->device_list, group_item)
 		iopt_remove_reserved_iova(&hwpt->ioas->iopt, cur->dev);
diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c
index 47ec7ddd5f5d..d6d550c3d0cc 100644
--- a/drivers/iommu/iommufd/hw_pagetable.c
+++ b/drivers/iommu/iommufd/hw_pagetable.c
@@ -3,12 +3,16 @@
  * Copyright (c) 2021-2022, NVIDIA CORPORATION & AFFILIATES
  */
 #include <linux/iommu.h>
+#include <linux/eventfd.h>
 #include <uapi/linux/iommufd.h>
 
 #include "../iommu-priv.h"
 #include "iommufd_private.h"
 #include "iommufd_test.h"
 
+static struct hw_pgtable_fault *hw_pagetable_fault_alloc(int eventfd);
+static void hw_pagetable_fault_free(struct hw_pgtable_fault *fault);
+
 void iommufd_hw_pagetable_destroy(struct iommufd_object *obj)
 {
 	struct iommufd_hw_pagetable *hwpt =
@@ -27,6 +31,9 @@ void iommufd_hw_pagetable_destroy(struct iommufd_object *obj)
 
 	if (hwpt->parent)
 		refcount_dec(&hwpt->parent->obj.users);
+
+	if (hwpt->fault)
+		hw_pagetable_fault_free(hwpt->fault);
 	refcount_dec(&hwpt->ioas->obj.users);
 }
 
@@ -255,6 +262,11 @@ int iommufd_hwpt_alloc(struct iommufd_ucmd *ucmd)
 		goto out_put_pt;
 	}
 
+	if (!parent && (cmd->flags & IOMMU_HWPT_ALLOC_FLAGS_IOPF_CAPABLE)) {
+		rc = -EINVAL;
+		goto out_put_pt;
+	}
+
 	if (klen) {
 		if (!cmd->data_len) {
 			rc = -EINVAL;
@@ -282,6 +294,14 @@ int iommufd_hwpt_alloc(struct iommufd_ucmd *ucmd)
 		goto out_unlock;
 	}
 
+	if (cmd->flags & IOMMU_HWPT_ALLOC_FLAGS_IOPF_CAPABLE) {
+		hwpt->fault = hw_pagetable_fault_alloc(cmd->event_fd);
+		if (IS_ERR(hwpt->fault)) {
+			rc = PTR_ERR(hwpt->fault);
+			goto out_hwpt;
+		}
+	}
+
 	cmd->out_hwpt_id = hwpt->obj.id;
 	rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));
 	if (rc)
@@ -346,3 +366,38 @@ int iommufd_hwpt_invalidate(struct iommufd_ucmd *ucmd)
 	iommufd_put_object(&hwpt->obj);
 	return rc;
 }
+
+static struct hw_pgtable_fault *hw_pagetable_fault_alloc(int eventfd)
+{
+	struct hw_pgtable_fault *fault;
+	int rc;
+
+	fault = kzalloc(sizeof(*fault), GFP_KERNEL);
+	if (!fault)
+		return ERR_PTR(-ENOMEM);
+
+	INIT_LIST_HEAD(&fault->deliver);
+	INIT_LIST_HEAD(&fault->response);
+	mutex_init(&fault->mutex);
+
+	fault->trigger = eventfd_ctx_fdget(eventfd);
+	if (IS_ERR(fault->trigger)) {
+		rc = PTR_ERR(fault->trigger);
+		goto out_free;
+	}
+
+	return fault;
+
+out_free:
+	kfree(fault);
+	return ERR_PTR(rc);
+}
+
+static void hw_pagetable_fault_free(struct hw_pgtable_fault *fault)
+{
+	WARN_ON(!list_empty(&fault->deliver));
+	WARN_ON(!list_empty(&fault->response));
+
+	eventfd_ctx_put(fault->trigger);
+	kfree(fault);
+}
-- 
2.34.1