Re: [PATCH 1/2] iommu: Consolidate pasid dma ownership check

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On 2023/8/2 9:39, Tian, Kevin wrote:
From: Baolu Lu<baolu.lu@xxxxxxxxxxxxxxx>
Sent: Tuesday, August 1, 2023 3:44 PM

On 2023/8/1 15:03, Tian, Kevin wrote:
   /**
    * iommu_device_use_default_domain() - Device driver wants to handle
device
    *                                     DMA through the kernel DMA API.
@@ -3052,14 +3063,14 @@ int
iommu_device_use_default_domain(struct
device *dev)

   	mutex_lock(&group->mutex);
   	if (group->owner_cnt) {
-		if (group->owner || !iommu_is_default_domain(group) ||
-		    !xa_empty(&group->pasid_array)) {
+		if (group->owner || !iommu_is_default_domain(group)) {
   			ret = -EBUSY;
   			goto unlock_out;
   		}
   	}

   	group->owner_cnt++;
+	assert_pasid_dma_ownership(group);
Old code returns error if pasid_xrrary is not empty.

New code continues to take ownership with a warning.

this is a functional change. Is it intended or not?
If iommu_device_use_default_domain() is called with pasid_array not
empty, there must be a bug somewhere in the device driver. We should
WARN it instead of returning an error. Probably this is a functional
change? If so, I can add this in the commit message.

IMHO we should WARN*and*  return an error.

Okay, fine to me. Will make this in the next version.

Best regards,
baolu



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