drm/amdgpu:fix world switch hang

for SR-IOV, we must keep the pipeline-sync in the protection
of COND_EXEC, otherwise the command consumed by CPG is not
consistent when world switch triggerd, e.g.:

world switch hit and the IB frame is skipped so the fence
won't signal, thus CP will jump to the next DMAframe's pipeline-sync
command, and it will make CP hang foever.

after pipelin-sync moved into COND_EXEC the consistency can be
guaranteed

Signed-off-by: Monk Liu <Monk.Liu@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

3 files changed, 9 insertions, 5 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
index 1b30d2ab9c51..659997bfff30 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
@@ -130,6 +130,7 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned num_ibs,
 
         unsigned i;
         int r = 0;
+        bool need_pipe_sync = false;
 
         if (num_ibs == 0)
                 return -EINVAL;
@@ -165,7 +166,7 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned num_ibs,
         if (ring->funcs->emit_pipeline_sync && job &&
             ((tmp = amdgpu_sync_get_fence(&job->sched_sync)) ||
              amdgpu_vm_need_pipeline_sync(ring, job))) {
-                amdgpu_ring_emit_pipeline_sync(ring);
+                need_pipe_sync = true;
                 dma_fence_put(tmp);
         }
 
@@ -173,7 +174,7 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned num_ibs,
                 ring->funcs->insert_start(ring);
 
         if (job) {
-                r = amdgpu_vm_flush(ring, job);
+                r = amdgpu_vm_flush(ring, job, need_pipe_sync);
                 if (r) {
                         amdgpu_ring_undo(ring);
                         return r;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index cda9e5d8b831..30c4322ddce7 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -743,7 +743,7 @@ static bool amdgpu_vm_is_large_bar(struct amdgpu_device *adev)
  *
  * Emit a VM flush when it is necessary.
  */
-int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job)
+int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job, bool need_pipe_sync)
 {
         struct amdgpu_device *adev = ring->adev;
         unsigned vmhub = ring->funcs->vmhub;
@@ -765,12 +765,15 @@ int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job)
                 vm_flush_needed = true;
         }
 
-        if (!vm_flush_needed && !gds_switch_needed)
+        if (!vm_flush_needed && !gds_switch_needed && !need_pipe_sync)
                 return 0;
 
         if (ring->funcs->init_cond_exec)
                 patch_offset = amdgpu_ring_init_cond_exec(ring);
 
+        if (need_pipe_sync)
+                amdgpu_ring_emit_pipeline_sync(ring);
+
         if (ring->funcs->emit_vm_flush && vm_flush_needed) {
                 struct dma_fence *fence;
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
index 936f158bc5ec..3441ec58c823 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
@@ -222,7 +222,7 @@ int amdgpu_vm_alloc_pts(struct amdgpu_device *adev,
 int amdgpu_vm_grab_id(struct amdgpu_vm *vm, struct amdgpu_ring *ring,
                       struct amdgpu_sync *sync, struct dma_fence *fence,
                       struct amdgpu_job *job);
-int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job);
+int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job, bool need_pipe_sync);
 void amdgpu_vm_reset_id(struct amdgpu_device *adev, unsigned vmhub,
                         unsigned vmid);
 void amdgpu_vm_reset_all_ids(struct amdgpu_device *adev);