From: Joerg Roedel <[email protected]> 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: Joerg Roedel <[email protected]> Tested-by: Oded Gabbay <[email protected]> --- drivers/iommu/amd_iommu_v2.c | 40 +++++++++++++++++++++++++++++++++------- 1 file changed, 33 insertions(+), 7 deletions(-) diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c index 69a46f1..2b848c0 100644 --- a/drivers/iommu/amd_iommu_v2.c +++ b/drivers/iommu/amd_iommu_v2.c @@ -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 */ - mmu_notifier_unregister(&pasid_state->mn, pasid_state->mm); + /* + * 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 */ -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
