iommu/amd: Improve amd_iommu_v2_exit()

During module exit, the current logic loops through all possible
16-bit device ID space to search for existing devices and clean up
device state structures. This can be simplified by looping through
the device state list.

Also, refactor various clean up logic into free_device_state()
for better reusability.

Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Link: https://lore.kernel.org/r/20220301085626.87680-6-vasant.hegde@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/amd/iommu_v2.c

@@ -24,7 +24,6 @@
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Joerg Roedel <jroedel@suse.de>");
 
-#define MAX_DEVICES		0x10000
 #define PRI_QUEUE_SIZE		512
 
 struct pri_queue {
@@ -124,6 +123,15 @@ static void free_device_state(struct device_state *dev_state)
 {
 	struct iommu_group *group;
 
+	/* Get rid of any remaining pasid states */
+	free_pasid_states(dev_state);
+
+	/*
+	 * Wait until the last reference is dropped before freeing
+	 * the device state.
+	 */
+	wait_event(dev_state->wq, !atomic_read(&dev_state->count));
+
 	/*
 	 * First detach device from domain - No more PRI requests will arrive
 	 * from that device after it is unbound from the IOMMUv2 domain.
@@ -849,15 +857,7 @@ void amd_iommu_free_device(struct pci_dev *pdev)
 
 	spin_unlock_irqrestore(&state_lock, flags);
 
-	/* Get rid of any remaining pasid states */
-	free_pasid_states(dev_state);
-
 	put_device_state(dev_state);
-	/*
-	 * Wait until the last reference is dropped before freeing
-	 * the device state.
-	 */
-	wait_event(dev_state->wq, !atomic_read(&dev_state->count));
 	free_device_state(dev_state);
 }
 EXPORT_SYMBOL(amd_iommu_free_device);
@@ -954,8 +954,8 @@ out:
 
 static void __exit amd_iommu_v2_exit(void)
 {
-	struct device_state *dev_state;
-	int i;
+	struct device_state *dev_state, *next;
+	unsigned long flags;
 
 	if (!amd_iommu_v2_supported())
 		return;
@@ -968,18 +968,18 @@ static void __exit amd_iommu_v2_exit(void)
 	 * The loop below might call flush_workqueue(), so call
 	 * destroy_workqueue() after it
 	 */
-	for (i = 0; i < MAX_DEVICES; ++i) {
-		dev_state = get_device_state(i);
-
-		if (dev_state == NULL)
-			continue;
+	spin_lock_irqsave(&state_lock, flags);
 
+	list_for_each_entry_safe(dev_state, next, &state_list, list) {
 		WARN_ON_ONCE(1);
 
 		put_device_state(dev_state);
-		amd_iommu_free_device(dev_state->pdev);
+		list_del(&dev_state->list);
+		free_device_state(dev_state);
 	}
 
+	spin_unlock_irqrestore(&state_lock, flags);
+
 	destroy_workqueue(iommu_wq);
 }