iommu/amd: Don't set pasid_state->mm to NULL in unbind_pasid

With calling te mmu_notifier_register function we hold a
reference to the mm_struct that needs to be released in
mmu_notifier_unregister. This is true even if the notifier
was already unregistered from exit_mmap and the .release
call-back has already run.

So make sure we call mmu_notifier_unregister unconditionally
in amd_iommu_unbind_pasid.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Tested-by: Oded Gabbay <oded.gabbay@amd.com>

diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
index a195c78b63c6e5971872cb1ff6628c0b8600a458..2b7de882e91c4c5cf3b54f2d2e1ea371b8219190 100644 (file)
--- a/drivers/iommu/amd_iommu_v2.c
+++ b/drivers/iommu/amd_iommu_v2.c
@@ -320,13 +320,6 @@ 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)
@@ -756,17 +749,10 @@ void amd_iommu_unbind_pasid(struct pci_dev *pdev, int pasid)
        clear_pasid_state(dev_state, pasid_state->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.
+        * Call mmu_notifier_unregister to drop our reference
+        * to pasid_state->mm
         */
-       if (pasid_state->mm) {
-               /*
-                * This will call the mn_release function and unbind
-                * the PASID.
-                */
-               mmu_notifier_unregister(&pasid_state->mn, pasid_state->mm);
-       }
+       mmu_notifier_unregister(&pasid_state->mn, pasid_state->mm);
 
        put_pasid_state_wait(pasid_state); /* Reference taken in
                                              amd_iommu_pasid_bind */