Re: [PATCH v2 08/12] iommu: Prepare for separating SVA and IOPF

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On 2023/8/3 16:16, Tian, Kevin wrote:
From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Sent: Thursday, July 27, 2023 1:49 PM

@@ -82,7 +82,7 @@ static void iopf_handler(struct work_struct *work)
  	if (!domain || !domain->iopf_handler)
  		status = IOMMU_PAGE_RESP_INVALID;

-	list_for_each_entry_safe(iopf, next, &group->faults, list) {
+	list_for_each_entry(iopf, &group->faults, list) {
  		/*
  		 * For the moment, errors are sticky: don't handle
subsequent
  		 * faults in the group if there is an error.
@@ -90,14 +90,20 @@ static void iopf_handler(struct work_struct *work)
  		if (status == IOMMU_PAGE_RESP_SUCCESS)
  			status = domain->iopf_handler(&iopf->fault,
  						      domain->fault_data);
-
-		if (!(iopf->fault.prm.flags &
-		      IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE))
-			kfree(iopf);
  	}

  	iopf_complete_group(group->dev, &group->last_fault, status);
-	kfree(group);
+	iopf_free_group(group);
+}

this is perf-critical path. It's not good to traverse the list twice.

Freeing the fault group is not critical anymore, right?


+
+static int iopf_queue_work(struct iopf_group *group, work_func_t func)
+{
+	struct iopf_device_param *iopf_param = group->dev->iommu-
iopf_param;
+
+	INIT_WORK(&group->work, func);
+	queue_work(iopf_param->queue->wq, &group->work);
+
+	return 0;
  }

Is there plan to introduce further error in the future? otherwise this should
be void.

queue_work() return true or false. I should check and return the value.


btw the work queue is only for sva. If there is no other caller this can be
just kept in iommu-sva.c. No need to create a helper.

The definition of struct iopf_device_param is in this file. So I added a
helper to avoid making iopf_device_param visible globally.


@@ -199,8 +204,11 @@ int iommu_queue_iopf(struct iommu_fault *fault,
struct device *dev)
  			list_move(&iopf->list, &group->faults);
  	}

-	queue_work(iopf_param->queue->wq, &group->work);
-	return 0;
+	ret = iopf_queue_work(group, iopf_handler);
+	if (ret)
+		iopf_free_group(group);
+
+	return ret;


Here we can document that the iopf handler (in patch10) should free the
group, allowing the optimization inside the handler.

Yeah!

Best regards,
baolu



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