[PATCH 2/2] drm/amdgpu: use DRM_SCHED_FENCE_DONT_PIPELINE for VM updates

[Christian König]

Make sure that we always have a CPU round trip to let the submission
code correctly decide if a TLB flush is necessary or not.

Signed-off-by: Christian König <christian.koenig at amd.com>
CC: stable at vger.kernel.org # 5.19+
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vm_sdma.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_sdma.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_sdma.c
index 2b0669c464f6..69e105fa41f6 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_sdma.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_sdma.c
@@ -116,8 +116,15 @@ static int amdgpu_vm_sdma_commit(struct amdgpu_vm_update_params *p,
 				   DMA_RESV_USAGE_BOOKKEEP);
 	}
 
-	if (fence && !p->immediate)
+	if (fence && !p->immediate) {
+		/*
+		 * Most hw generations now have a separate queue for page table
+		 * updates, but when the queue is shared with userspace we need
+		 * the extra CPU round trip to correctly flush the TLB.
+		 */
+		set_bit(DRM_SCHED_FENCE_DONT_PIPELINE, &f->flags);
 		swap(*fence, f);
+	}
 	dma_fence_put(f);
 	return 0;
 
-- 
2.25.1