[PATCH 4.4 072/146] drm/amdkfd: unbind only existing processes

Greg Kroah-Hartman
2016-07-25T21:17:13Z

From: Oded Gabbay <oded.gabbay@gmail.com>

commit 121b78e679ee3ffab780115e260b2775d0cc1f73 upstream.

When unbinding a process from a device (initiated by amd_iommu_v2), the
driver needs to make sure that process still exists in the process table.
There is a possibility that amdkfd's own notifier handler -
kfd_process_notifier_release() - was called before the unbind function
and it already removed the process from the process table.

v2:
Because there can be only one process with the specified pasid, and
because *p can't be NULL inside the hash_for_each_rcu macro, it is more
reasonable to just put the whole code inside the if statement that
compares the pasid value. That way, when we exit hash_for_each_rcu, we
simply exit the function as well.

Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/gpu/drm/amd/amdkfd/kfd_process.c | 60 ++++++++++++++++++-------------
1 file changed, 35 insertions(+), 25 deletions(-)

--- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
@@ -404,42 +404,52 @@ void kfd_unbind_process_from_device(stru

idx = srcu_read_lock(&kfd_processes_srcu);

+ /*
+ * Look for the process that matches the pasid. If there is no such
+ * process, we either released it in amdkfd's own notifier, or there
+ * is a bug. Unfortunately, there is no way to tell...
+ */
hash_for_each_rcu(kfd_processes_table, i, p, kfd_processes)
- if (p->pasid == pasid)
- break;
+ if (p->pasid == pasid) {

- srcu_read_unlock(&kfd_processes_srcu, idx);
+ srcu_read_unlock(&kfd_processes_srcu, idx);

- BUG_ON(p->pasid != pasid);
+ pr_debug("Unbinding process %d from IOMMU\n", pasid);

- mutex_lock(&p->mutex);
+ mutex_lock(&p->mutex);

- if ((dev->dbgmgr) && (dev->dbgmgr->pasid == p->pasid))
- kfd_dbgmgr_destroy(dev->dbgmgr);
+ if ((dev->dbgmgr) && (dev->dbgmgr->pasid == p->pasid))
+ kfd_dbgmgr_destroy(dev->dbgmgr);

- pqm_uninit(&p->pqm);
+ pqm_uninit(&p->pqm);

- pdd = kfd_get_process_device_data(dev, p);
+ pdd = kfd_get_process_device_data(dev, p);

- if (!pdd) {
- mutex_unlock(&p->mutex);
- return;
- }
+ if (!pdd) {
+ mutex_unlock(&p->mutex);
+ return;
+ }

- if (pdd->reset_wavefronts) {
- dbgdev_wave_reset_wavefronts(pdd->dev, p);
- pdd->reset_wavefronts = false;
- }
+ if (pdd->reset_wavefronts) {
+ dbgdev_wave_reset_wavefronts(pdd->dev, p);
+ pdd->reset_wavefronts = false;
+ }

- /*
- * Just mark pdd as unbound, because we still need it to call
- * amd_iommu_unbind_pasid() in when the process exits.
- * We don't call amd_iommu_unbind_pasid() here
- * because the IOMMU called us.
- */
- pdd->bound = false;
+ /*
+ * Just mark pdd as unbound, because we still need it
+ * to call amd_iommu_unbind_pasid() in when the
+ * process exits.
+ * We don't call amd_iommu_unbind_pasid() here
+ * because the IOMMU called us.
+ */
+ pdd->bound = false;
+
+ mutex_unlock(&p->mutex);

- mutex_unlock(&p->mutex);
+ return;
+ }
+
+ srcu_read_unlock(&kfd_processes_srcu, idx);
}

struct kfd_process_device *kfd_get_first_process_device_data(struct kfd_process *p)