[PATCH 2/2] iommu: Swap the order of setting group->pasid_array and __iommu_set_group_pasid()

[Yi Liu <yi.l.liu@intel.com>]

Following the current order of setting group->pasid_array and
__iommu_set_group_pasid() in iommu_attach_device_pasid(), PRIs may be
forwarded to the domain before the attach succeeds. If the attach failed
in the end, the PRIs on the domain need to be flushed in the caller side.
Caller can do it, but it can be avoided by swapping the order. This is
more self-contained.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
 drivers/iommu/iommu.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 278c4eb8f225..b69bcf559839 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -3376,7 +3376,7 @@ int iommu_attach_device_pasid(struct iommu_domain *domain,
 	struct iommu_group *group = dev->iommu_group;
 	struct group_device *device;
 	const struct iommu_ops *ops;
-	void *xa_entry;
+	void *curr, *xa_entry;
 	int ret;
 
 	if (!group)
@@ -3400,6 +3400,16 @@ int iommu_attach_device_pasid(struct iommu_domain *domain,
 		}
 	}
 
+	curr = xa_load(&group->pasid_array, pasid);
+	if (curr) {
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+
+	ret = __iommu_set_group_pasid(domain, group, pasid);
+	if (ret)
+		goto out_unlock;
+
 	if (handle) {
 		handle->domain = domain;
 		xa_entry = xa_tag_pointer(handle, IOMMU_PASID_ARRAY_HANDLE);
@@ -3407,13 +3417,12 @@ int iommu_attach_device_pasid(struct iommu_domain *domain,
 		xa_entry = xa_tag_pointer(domain, IOMMU_PASID_ARRAY_DOMAIN);
 	}
 
-	ret = xa_insert(&group->pasid_array, pasid, xa_entry, GFP_KERNEL);
-	if (ret)
-		goto out_unlock;
+	curr = xa_store(&group->pasid_array, pasid, handle, GFP_KERNEL);
+	if (curr) {
+		__iommu_remove_group_pasid(group, pasid, domain);
+		ret = xa_err(curr);
+	}
 
-	ret = __iommu_set_group_pasid(domain, group, pasid);
-	if (ret)
-		xa_erase(&group->pasid_array, pasid);
 out_unlock:
 	mutex_unlock(&group->mutex);
 	return ret;
-- 
2.34.1