[PATCH v10 13/16] iommu: Improve iopf_queue_remove_device()

Lu Baolu
2024-01-22T05:49:28Z

Convert iopf_queue_remove_device() to return void instead of an error code,
as the return value is never used. This removal helper is designed to be
never-failed, so there's no need for error handling.

Ack all outstanding page requests from the device with the response code of
IOMMU_PAGE_RESP_INVALID, indicating device should not attempt any retry.

Add comments to this helper explaining the steps involved in removing a
device from the iopf queue and disabling its PRI.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Tested-by: Yan Zhao <yan.y.zhao@intel.com>
---
include/linux/iommu.h | 5 ++--
drivers/iommu/intel/iommu.c | 7 +----
drivers/iommu/io-pgfault.c | 59 ++++++++++++++++++++++++-------------
3 files changed, 41 insertions(+), 30 deletions(-)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 396d7b0d88b2..d9a99a978ffa 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -1542,7 +1542,7 @@ iommu_sva_domain_alloc(struct device *dev, struct mm_struct *mm)

#ifdef CONFIG_IOMMU_IOPF
int iopf_queue_add_device(struct iopf_queue *queue, struct device *dev);
-int iopf_queue_remove_device(struct iopf_queue *queue, struct device *dev);
+void iopf_queue_remove_device(struct iopf_queue *queue, struct device *dev);
int iopf_queue_flush_dev(struct device *dev);
struct iopf_queue *iopf_queue_alloc(const char *name);
void iopf_queue_free(struct iopf_queue *queue);
@@ -1558,10 +1558,9 @@ iopf_queue_add_device(struct iopf_queue *queue, struct device *dev)
return -ENODEV;
}

-static inline int
+static inline void
iopf_queue_remove_device(struct iopf_queue *queue, struct device *dev)
{
- return -ENODEV;
}

static inline int iopf_queue_flush_dev(struct device *dev)
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 29a12f289e2e..a81a2be9b870 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4455,12 +4455,7 @@ static int intel_iommu_disable_iopf(struct device *dev)
*/
pci_disable_pri(to_pci_dev(dev));
info->pri_enabled = 0;
-
- /*
- * With PRI disabled and outstanding PRQs drained, removing device
- * from iopf queue should never fail.
- */
- WARN_ON(iopf_queue_remove_device(iommu->iopf_queue, dev));
+ iopf_queue_remove_device(iommu->iopf_queue, dev);

return 0;
}
diff --git a/drivers/iommu/io-pgfault.c b/drivers/iommu/io-pgfault.c
index ce7058892b59..26e100ca3221 100644
--- a/drivers/iommu/io-pgfault.c
+++ b/drivers/iommu/io-pgfault.c
@@ -448,50 +448,67 @@ EXPORT_SYMBOL_GPL(iopf_queue_add_device);
* @queue: IOPF queue
* @dev: device to remove
*
- * Caller makes sure that no more faults are reported for this device.
+ * Removing a device from an iopf_queue. It's recommended to follow these
+ * steps when removing a device:
*
- * Return: 0 on success and <0 on error.
+ * - 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.
+ * - Tear down the iopf infrastructure: 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().
*/
-int iopf_queue_remove_device(struct iopf_queue *queue, struct device *dev)
+void iopf_queue_remove_device(struct iopf_queue *queue, struct device *dev)
{
- int ret = 0;
struct iopf_fault *iopf, *next;
+ struct iommu_page_response resp;
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(&param->lock);
fault_param = rcu_dereference_check(param->fault_param,
lockdep_is_held(&param->lock));
- if (!fault_param) {
- ret = -ENODEV;
- goto unlock;
- }
-
- if (fault_param->queue != queue) {
- ret = -EINVAL;
- goto unlock;
- }

- if (!list_empty(&fault_param->faults)) {
- ret = -EBUSY;
+ if (WARN_ON(!fault_param || fault_param->queue != queue))
goto unlock;
- }
-
- list_del(&fault_param->queue_list);

- /* Just in case some faults are still stuck */
+ mutex_lock(&fault_param->lock);
list_for_each_entry_safe(iopf, next, &fault_param->partial, list)
kfree(iopf);

+ list_for_each_entry_safe(iopf, next, &fault_param->faults, list) {
+ memset(&resp, 0, sizeof(struct iommu_page_response));
+ resp.pasid = iopf->fault.prm.pasid;
+ resp.grpid = iopf->fault.prm.grpid;
+ resp.code = IOMMU_PAGE_RESP_INVALID;
+
+ if (iopf->fault.prm.flags & IOMMU_FAULT_PAGE_RESPONSE_NEEDS_PASID)
+ resp.flags = IOMMU_PAGE_RESP_PASID_VALID;
+
+ ops->page_response(dev, iopf, &resp);
+ list_del(&iopf->list);
+ kfree(iopf);
+ }
+ 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(&param->lock);
mutex_unlock(&queue->lock);
-
- return ret;
}
EXPORT_SYMBOL_GPL(iopf_queue_remove_device);

--
2.34.1