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Commit f0aac63b authored by Joerg Roedel's avatar Joerg Roedel
Browse files

iommu/amd: Don't hold a reference to mm_struct 



With mmu_notifiers we don't need to hold a reference to the
mm_struct during the time the pasid is bound to a device. We
can rely on the .mn_release call back to inform us when the
mm_struct goes away.

Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
Tested-by: default avatarOded Gabbay <Oded.Gabbay@amd.com>
parent 53d340ef

drivers/iommu/amd_iommu_v2.c

+33 −7
Original line number Diff line number Diff line
@@ -297,7 +297,6 @@ static void put_pasid_state_wait(struct pasid_state *pasid_state) 
		schedule();



	finish_wait(&pasid_state->wq, &wait);

	mmput(pasid_state->mm);

	free_pasid_state(pasid_state);

}
@@ -321,6 +320,13 @@ static void unbind_pasid(struct pasid_state *pasid_state) 


	/* Make sure no more pending faults are in the queue */

	flush_workqueue(iommu_wq);



	/*

	 * No more faults are in the work queue and no new faults will be queued

	 * from here on. We can safely set pasid_state->mm to NULL now as the

	 * mm_struct might go away after we return.

	 */

	pasid_state->mm = NULL;

}



static void free_pasid_states_level1(struct pasid_state **tbl)
@@ -636,6 +642,7 @@ int amd_iommu_bind_pasid(struct pci_dev *pdev, int pasid, 
{

	struct pasid_state *pasid_state;

	struct device_state *dev_state;

	struct mm_struct *mm;

	u16 devid;

	int ret;
@@ -659,12 +666,14 @@ int amd_iommu_bind_pasid(struct pci_dev *pdev, int pasid, 
	if (pasid_state == NULL)

		goto out;





	atomic_set(&pasid_state->count, 1);

	init_waitqueue_head(&pasid_state->wq);

	spin_lock_init(&pasid_state->lock);



	mm                        = get_task_mm(task);

	pasid_state->task         = task;

	pasid_state->mm           = get_task_mm(task);

	pasid_state->mm           = mm;

	pasid_state->device_state = dev_state;

	pasid_state->pasid        = pasid;

	pasid_state->invalid      = false;
@@ -673,7 +682,7 @@ int amd_iommu_bind_pasid(struct pci_dev *pdev, int pasid, 
	if (pasid_state->mm == NULL)

		goto out_free;



	mmu_notifier_register(&pasid_state->mn, pasid_state->mm);

	mmu_notifier_register(&pasid_state->mn, mm);



	ret = set_pasid_state(dev_state, pasid_state, pasid);

	if (ret)
@@ -684,16 +693,23 @@ int amd_iommu_bind_pasid(struct pci_dev *pdev, int pasid, 
	if (ret)

		goto out_clear_state;



	/*

	 * Drop the reference to the mm_struct here. We rely on the

	 * mmu_notifier release call-back to inform us when the mm

	 * is going away.

	 */

	mmput(mm);



	return 0;



out_clear_state:

	clear_pasid_state(dev_state, pasid);



out_unregister:

	mmu_notifier_unregister(&pasid_state->mn, pasid_state->mm);

	mmu_notifier_unregister(&pasid_state->mn, mm);



out_free:

	mmput(pasid_state->mm);

	mmput(mm);

	free_pasid_state(pasid_state);



out:
@@ -734,8 +750,18 @@ void amd_iommu_unbind_pasid(struct pci_dev *pdev, int pasid) 
	/* Clear the pasid state so that the pasid can be re-used */

	clear_pasid_state(dev_state, pasid_state->pasid);



	/* This will call the mn_release function and unbind the PASID */

	/*

	 * Check if pasid_state->mm is still valid. If mn_release has already

	 * run it will be NULL and we can't (and don't need to) call

	 * mmu_notifier_unregister() on it anymore.

	 */

	if (pasid_state->mm) {

		/*

		 * This will call the mn_release function and unbind

		 * the PASID.

		 */

		mmu_notifier_unregister(&pasid_state->mn, pasid_state->mm);

	}



	put_pasid_state_wait(pasid_state); /* Reference taken in

					      amd_iommu_pasid_bind */