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

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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 <jroedel@suse.de>
Tested-by: Oded Gabbay <Oded.Gabbay@amd.com>
This commit is contained in:
Joerg Roedel 2014-07-08 15:15:07 +02:00
parent 53d340ef4a
commit f0aac63b87
1 changed files with 33 additions and 7 deletions
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40
drivers/iommu/amd_iommu_v2.c
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@ -297,7 +297,6 @@ static void put_pasid_state_wait(struct pasid_state *pasid_state)
schedule(); schedule();
finish_wait(&pasid_state->wq, &wait); finish_wait(&pasid_state->wq, &wait);
mmput(pasid_state->mm);
free_pasid_state(pasid_state); 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 */ /* Make sure no more pending faults are in the queue */
flush_workqueue(iommu_wq); 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) 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 pasid_state *pasid_state;
struct device_state *dev_state; struct device_state *dev_state;
struct mm_struct *mm;
u16 devid; u16 devid;
int ret; int ret;
@ -659,12 +666,14 @@ int amd_iommu_bind_pasid(struct pci_dev *pdev, int pasid,
if (pasid_state == NULL) if (pasid_state == NULL)
goto out; goto out;
atomic_set(&pasid_state->count, 1); atomic_set(&pasid_state->count, 1);
init_waitqueue_head(&pasid_state->wq); init_waitqueue_head(&pasid_state->wq);
spin_lock_init(&pasid_state->lock); spin_lock_init(&pasid_state->lock);
mm = get_task_mm(task);
pasid_state->task = task; pasid_state->task = task;
pasid_state->mm = get_task_mm(task); pasid_state->mm = mm;
pasid_state->device_state = dev_state; pasid_state->device_state = dev_state;
pasid_state->pasid = pasid; pasid_state->pasid = pasid;
pasid_state->invalid = false; pasid_state->invalid = false;
@ -673,7 +682,7 @@ int amd_iommu_bind_pasid(struct pci_dev *pdev, int pasid,
if (pasid_state->mm == NULL) if (pasid_state->mm == NULL)
goto out_free; 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); ret = set_pasid_state(dev_state, pasid_state, pasid);
if (ret) if (ret)
@ -684,16 +693,23 @@ int amd_iommu_bind_pasid(struct pci_dev *pdev, int pasid,
if (ret) if (ret)
goto out_clear_state; 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; return 0;
out_clear_state: out_clear_state:
clear_pasid_state(dev_state, pasid); clear_pasid_state(dev_state, pasid);
out_unregister: out_unregister:
mmu_notifier_unregister(&pasid_state->mn, pasid_state->mm); mmu_notifier_unregister(&pasid_state->mn, mm);
out_free: out_free:
mmput(pasid_state->mm); mmput(mm);
free_pasid_state(pasid_state); free_pasid_state(pasid_state);
out: 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 the pasid state so that the pasid can be re-used */
clear_pasid_state(dev_state, pasid_state->pasid); 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 put_pasid_state_wait(pasid_state); /* Reference taken in
amd_iommu_pasid_bind */ amd_iommu_pasid_bind */