// SPDX-License-Identifier: GPL-2.0
/*
* Handle device page faults
*
* Copyright (C) 2020 ARM Ltd.
*/
#include <linux/iommu.h>
#include <linux/list.h>
#include <linux/sched/mm.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include "iommu-priv.h"
/*
* Return the fault parameter of a device if it exists. Otherwise, return NULL.
* On a successful return, the caller takes a reference of this parameter and
* should put it after use by calling iopf_put_dev_fault_param().
*/
static struct iommu_fault_param *iopf_get_dev_fault_param(struct device *dev)
{
struct dev_iommu *param = dev->iommu;
struct iommu_fault_param *fault_param;
rcu_read_lock();
fault_param = rcu_dereference(param->fault_param);
if (fault_param && !refcount_inc_not_zero(&fault_param->users))
fault_param = NULL;
rcu_read_unlock();
return fault_param;
}
/* Caller must hold a reference of the fault parameter. */
static void iopf_put_dev_fault_param(struct iommu_fault_param *fault_param)
{
if (refcount_dec_and_test(&fault_param->users))
kfree_rcu(fault_param, rcu);
}
static void __iopf_free_group(struct iopf_group *group)
{
struct iopf_fault *iopf, *next;
list_for_each_entry_safe(iopf, next, &group->faults, list) {
if (!(iopf->fault.prm.flags & IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE))
kfree(iopf);
}
/* Pair with iommu_report_device_fault(). */
iopf_put_dev_fault_param(group->fault_param);
}
void iopf_free_group(struct iopf_group *group)
{
__iopf_free_group(group);
kfree(group);
}
EXPORT_SYMBOL_GPL(iopf_free_group);
/* Non-last request of a group. Postpone until the last one. */
static int report_partial_fault(struct iommu_fault_param *fault_param,
struct iommu_fault *fault)
{
struct iopf_fault *iopf;
iopf = kzalloc(sizeof(*iopf), GFP_KERNEL);
if (!iopf)
return -ENOMEM;
iopf->fault = *fault;
mutex_lock(&fault_param->lock);
list_add(&iopf->list, &fault_param->partial);
mutex_unlock(&fault_param->lock);
return 0;
}
static struct iopf_group *iopf_group_alloc(struct iommu_fault_param *iopf_param,
struct iopf_fault *evt,
struct iopf_group *abort_group)
{
struct iopf_fault *iopf, *next;
struct iopf_group *group;
group = kzalloc(sizeof(*group), GFP_KERNEL);
if (!group) {
/*
* We always need to construct the group as we need it to abort
* the request at the driver if it can't be handled.
*/
group = abort_group;
}
group->fault_param = iopf_param;
group->last_fault.fault = evt->fault;
INIT_LIST_HEAD(&group->faults);
INIT_LIST_HEAD(&group->pending_node);
list_add(&group->last_fault.list, &group->faults);
/* See if we have partial faults for this group */
mutex_lock(&iopf_param->lock);
list_for_each_entry_safe(iopf, next, &iopf_param->partial, list) {
if (iopf->fault.prm.grpid == evt->fault.prm.grpid)
/* Insert *before* the last fault */
list_move(&iopf->list, &group->faults);
}
list_add(&group->pending_node, &iopf_param->faults);
mutex_unlock(&iopf_param->lock);
group->fault_count = list_count_nodes(&group->faults);
return group;
}
static struct iommu_attach_handle *find_fault_handler(struct device *dev,
struct iopf_fault *evt)
{
struct iommu_fault *fault = &evt->fault;
struct iommu_attach_handle *attach_handle;
if (fault->prm.flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID) {
attach_handle = iommu_attach_handle_get(dev->iommu_group,
fault->prm.pasid, 0);
if (IS_ERR(attach_handle)) {
const struct iommu_ops *ops = dev_iommu_ops(dev);
if (!ops->user_pasid_table)
return NULL;
/*
* The iommu driver for this device supports user-
* managed PASID table. Therefore page faults for
* any PASID should go through the NESTING domain
* attached to the device RID.
*/
attach_handle = iommu_attach_handle_get(
dev->iommu_group, IOMMU_NO_PASID,
IOMMU_DOMAIN_NESTED);
if (IS_ERR(attach_handle))
return NULL;
}
} else {
attach_handle = iommu_attach_handle_get(dev->iommu_group,
IOMMU_NO_PASID, 0);
if (IS_ERR(attach_handle))
return NULL;
}
if (!attach_handle->domain->iopf_handler)
return NULL;
return attach_handle;
}
static void iopf_error_response(struct device *dev, struct iopf_fault *evt)
{
const struct iommu_ops *ops = dev_iommu_ops(dev);
struct iommu_fault *fault = &evt->fault;
struct iommu_page_response resp = {
.pasid = fault->prm.pasid,
.grpid = fault->prm.grpid,
.code = IOMMU_PAGE_RESP_INVALID
};
ops->page_response(dev, evt, &resp);
}
/**
* iommu_report_device_fault() - Report fault event to device driver
* @dev: the device
* @evt: fault event data
*
* Called by IOMMU drivers when a fault is detected, typically in a threaded IRQ
* handler. If this function fails then ops->page_response() was called to
* complete evt if required.
*
* This module doesn't handle PCI PASID Stop Marker; IOMMU drivers must discard
* them before reporting faults. A PASID Stop Marker (LRW = 0b100) doesn't
* expect a response. It may be generated when disabling a PASID (issuing a
* PASID stop request) by some PCI devices.
*
* The PASID stop request is issued by the device driver before unbind(). Once
* it completes, no page request is generated for this PASID anymore and
* outstanding ones have been pushed to the IOMMU (as per PCIe 4.0r1.0 - 6.20.1
* and 10.4.1.2 - Managing PASID TLP Prefix Usage). Some PCI devices will wait
* for all outstanding page requests to come back with a response before
* completing the PASID stop request. Others do not wait for page responses, and
* instead issue this Stop Marker that tells us when the PASID can be
* reallocated.
*
* It is safe to discard the Stop Marker because it is an optimization.
* a. Page requests, which are posted requests, have been flushed to the IOMMU
* when the stop request completes.
* b. The IOMMU driver flushes all fault queues on unbind() before freeing the
* PASID.
*
* So even though the Stop Marker might be issued by the device *after* the stop
* request completes, outstanding faults will have been dealt with by the time
* the PASID is freed.
*
* Any valid page fault will be eventually routed to an iommu domain and the
* page fault handler installed there will get called. The users of this
* handling framework should guarantee that the iommu domain could only be
* freed after the device has stopped generating page faults (or the iommu
* hardware has been set to block the page faults) and the pending page faults
* have been flushed. In case no page fault handler is attached or no iopf params
* are setup, then the ops->page_response() is called to complete the evt.
*
* Returns 0 on success, or an error in case of a bad/failed iopf setup.
*/
int iommu_report_device_fault(struct device *dev, struct iopf_fault *evt)
{
struct iommu_attach_handle *attach_handle;
struct iommu_fault *fault = &evt->fault;
struct iommu_fault_param *iopf_param;
struct iopf_group abort_group = {};
struct iopf_group *group;
attach_handle = find_fault_handler(dev, evt);
if (!attach_handle)
goto err_bad_iopf;
/*
* Something has gone wrong if a fault capable domain is attached but no
* iopf_param is setup
*/
iopf_param = iopf_get_dev_fault_param(dev);
if (WARN_ON(!iopf_param))
goto err_bad_iopf;
if (!(fault->prm.flags & IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE)) {
int ret;
ret = report_partial_fault(iopf_param, fault);
iopf_put_dev_fault_param(iopf_param);
/* A request that is not the last does not need to be ack'd */
return ret;
}
/*
* This is the last page fault of a group. Allocate an iopf group and
* pass it to domain's page fault handler. The group holds a reference
* count of the fault parameter. It will be released after response or
* error path of this function. If an error is returned, the caller
* will send a response to the hardware. We need to clean up before
* leaving, otherwise partial faults will be stuck.
*/
group = iopf_group_alloc(iopf_param, evt, &abort_group);
if (group == &abort_group)
goto err_abort;
group->attach_handle = attach_handle;
/*
* On success iopf_handler must call iopf_group_response() and
* iopf_free_group()
*/
if (group->attach_handle->domain->iopf_handler(group))
goto err_abort;
return 0;
err_abort:
dev_warn_ratelimited(dev, "iopf with pasid %d aborted\n",
fault->prm.pasid);
iopf_group_response(group, IOMMU_PAGE_RESP_FAILURE);
if (group == &abort_group)
__iopf_free_group(group);
else
iopf_free_group(group);
return 0;
err_bad_iopf:
if (fault->type == IOMMU_FAULT_PAGE_REQ)
iopf_error_response(dev, evt);
return -EINVAL;
}
EXPORT_SYMBOL_GPL(iommu_report_device_fault);
/**
* iopf_queue_flush_dev - Ensure that all queued faults have been processed
* @dev: the endpoint whose faults need to be flushed.
*
* The IOMMU driver calls this before releasing a PASID, to ensure that all
* pending faults for this PASID have been handled, and won't hit the address
* space of the next process that uses this PASID. The driver must make sure
* that no new fault is added to the queue. In particular it must flush its
* low-level queue before calling this function.
*
* Return: 0 on success and <0 on error.
*/
int iopf_queue_flush_dev(struct device *dev)
{
struct iommu_fault_param *iopf_param;
/*
* It's a driver bug to be here after iopf_queue_remove_device().
* Therefore, it's safe to dereference the fault parameter without
* holding the lock.
*/
iopf_param = rcu_dereference_check(dev->iommu->fault_param, true);
if (WARN_ON(!iopf_param))
return -ENODEV;
flush_workqueue(iopf_param->queue->wq);
return 0;
}
EXPORT_SYMBOL_GPL(iopf_queue_flush_dev);
/**
* iopf_group_response - Respond a group of page faults
* @group: the group of faults with the same group id
* @status: the response code
*/
void iopf_group_response(struct iopf_group *group,
enum iommu_page_response_code status)
{
struct iommu_fault_param *fault_param = group->fault_param;
struct iopf_fault *iopf = &group->last_fault;
struct device *dev = group->fault_param->dev;
const struct iommu_ops *ops = dev_iommu_ops(dev);
struct iommu_page_response resp = {
.pasid = iopf->fault.prm.pasid,
.grpid = iopf->fault.prm.grpid,
.code = status,
};
/* Only send response if there is a fault report pending */
mutex_lock(&fault_param->lock);
if (!list_empty(&group->pending_node)) {
ops->page_response(dev, &group->last_fault, &resp);
list_del_init(&group->pending_node);
}
mutex_unlock(&fault_param->lock);
}
EXPORT_SYMBOL_GPL(iopf_group_response);
/**
* iopf_queue_discard_partial - Remove all pending partial fault
* @queue: the queue whose partial faults need to be discarded
*
* When the hardware queue overflows, last page faults in a group may have been
* lost and the IOMMU driver calls this to discard all partial faults. The
* driver shouldn't be adding new faults to this queue concurrently.
*
* Return: 0 on success and <0 on error.
*/
int iopf_queue_discard_partial(struct iopf_queue *queue)
{
struct iopf_fault *iopf, *next;
struct iommu_fault_param *iopf_param;
if (!queue)
return -EINVAL;
mutex_lock(&queue->lock);
list_for_each_entry(iopf_param, &queue->devices, queue_list) {
mutex_lock(&iopf_param->lock);
list_for_each_entry_safe(iopf, next, &iopf_param->partial,
list) {
list_del(&iopf->list);
kfree(iopf);
}
mutex_unlock(&iopf_param->lock);
}
mutex_unlock(&queue->lock);
return 0;
}
EXPORT_SYMBOL_GPL(iopf_queue_discard_partial);
/**
* iopf_queue_add_device - Add producer to the fault queue
* @queue: IOPF queue
* @dev: device to add
*
* Return: 0 on success and <0 on error.
*/
int iopf_queue_add_device(struct iopf_queue *queue, struct device *dev)
{
int ret = 0;
struct dev_iommu *param = dev->iommu;
struct iommu_fault_param *fault_param;
const struct iommu_ops *ops = dev_iommu_ops(dev);
if (!ops->page_response)
return -ENODEV;
mutex_lock(&queue->lock);
mutex_lock(¶m->lock);
if (rcu_dereference_check(param->fault_param,
lockdep_is_held(¶m->lock))) {
ret = -EBUSY;
goto done_unlock;
}
fault_param = kzalloc(sizeof(*fault_param), GFP_KERNEL);
if (!fault_param) {
ret = -ENOMEM;
goto done_unlock;
}
mutex_init(&fault_param->lock);
INIT_LIST_HEAD(&fault_param->faults);
INIT_LIST_HEAD(&fault_param->partial);
fault_param->dev = dev;
refcount_set(&fault_param->users, 1);
list_add(&fault_param->queue_list, &queue->devices);
fault_param->queue = queue;
rcu_assign_pointer(param->fault_param, fault_param);
done_unlock:
mutex_unlock(¶m->lock);
mutex_unlock(&queue->lock);
return ret;
}
EXPORT_SYMBOL_GPL(iopf_queue_add_device);
/**
* iopf_queue_remove_device - Remove producer from fault queue
* @queue: IOPF queue
* @dev: device to remove
*
* Removing a device from an iopf_queue. It's recommended to follow these
* steps when removing a device:
*
* - Disable new PRI reception: Turn off PRI generation in the IOMMU hardware
* and flush any hardware page request queues. This should be done before
* calling into this helper.
* - Acknowledge all outstanding PRQs to the device: Respond to all outstanding
* page requests with IOMMU_PAGE_RESP_INVALID, indicating the device should
* not retry. This helper function handles this.
* - Disable PRI on the device: After calling this helper, the caller could
* then disable PRI on the device.
*
* Calling iopf_queue_remove_device() essentially disassociates the device.
* The fault_param might still exist, but iommu_page_response() will do
* nothing. The device fault parameter reference count has been properly
* passed from iommu_report_device_fault() to the fault handling work, and
* will eventually be released after iommu_page_response().
*/
void iopf_queue_remove_device(struct iopf_queue *queue, struct device *dev)
{
struct iopf_fault *partial_iopf;
struct iopf_fault *next;
struct iopf_group *group, *temp;
struct dev_iommu *param = dev->iommu;
struct iommu_fault_param *fault_param;
const struct iommu_ops *ops = dev_iommu_ops(dev);
mutex_lock(&queue->lock);
mutex_lock(¶m->lock);
fault_param = rcu_dereference_check(param->fault_param,
lockdep_is_held(¶m->lock));
if (WARN_ON(!fault_param || fault_param->queue != queue))
goto unlock;
mutex_lock(&fault_param->lock);
list_for_each_entry_safe(partial_iopf, next, &fault_param->partial, list)
kfree(partial_iopf);
list_for_each_entry_safe(group, temp, &fault_param->faults, pending_node) {
struct iopf_fault *iopf = &group->last_fault;
struct iommu_page_response resp = {
.pasid = iopf->fault.prm.pasid,
.grpid = iopf->fault.prm.grpid,
.code = IOMMU_PAGE_RESP_INVALID
};
ops->page_response(dev, iopf, &resp);
list_del_init(&group->pending_node);
}
mutex_unlock(&fault_param->lock);
list_del(&fault_param->queue_list);
/* dec the ref owned by iopf_queue_add_device() */
rcu_assign_pointer(param->fault_param, NULL);
iopf_put_dev_fault_param(fault_param);
unlock:
mutex_unlock(¶m->lock);
mutex_unlock(&queue->lock);
}
EXPORT_SYMBOL_GPL(iopf_queue_remove_device);
/**
* iopf_queue_alloc - Allocate and initialize a fault queue
* @name: a unique string identifying the queue (for workqueue)
*
* Return: the queue on success and NULL on error.
*/
struct iopf_queue *iopf_queue_alloc(const char *name)
{
struct iopf_queue *queue;
queue = kzalloc(sizeof(*queue), GFP_KERNEL);
if (!queue)
return NULL;
/*
* The WQ is unordered because the low-level handler enqueues faults by
* group. PRI requests within a group have to be ordered, but once
* that's dealt with, the high-level function can handle groups out of
* order.
*/
queue->wq = alloc_workqueue("iopf_queue/%s", WQ_UNBOUND, 0, name);
if (!queue->wq) {
kfree(queue);
return NULL;
}
INIT_LIST_HEAD(&queue->devices);
mutex_init(&queue->lock);
return queue;
}
EXPORT_SYMBOL_GPL(iopf_queue_alloc);
/**
* iopf_queue_free - Free IOPF queue
* @queue: queue to free
*
* Counterpart to iopf_queue_alloc(). The driver must not be queuing faults or
* adding/removing devices on this queue anymore.
*/
void iopf_queue_free(struct iopf_queue *queue)
{
struct iommu_fault_param *iopf_param, *next;
if (!queue)
return;
list_for_each_entry_safe(iopf_param, next, &queue->devices, queue_list)
iopf_queue_remove_device(queue, iopf_param->dev);
destroy_workqueue(queue->wq);
kfree(queue);
}
EXPORT_SYMBOL_GPL(iopf_queue_free);
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