[PATCH for v4.9 LTS 42/86] drm/amdgpu: check ring being ready before using

[Levin, Alexander (Sasha Levin)]

From: Ding Pixel <pding@xxxxxxx>

[ Upstream commit c5f21c9f878b8dcd54d0b9739c025ca73cb4c091 ]

Return success when the ring is properly initialized, otherwise return
failure.

Tonga SRIOV VF doesn't have UVD and VCE engines, the initialization of
these IPs is bypassed. The system crashes if application submit IB to
their rings which are not ready to use. It could be a common issue if
IP having ring buffer is disabled for some reason on specific ASIC, so
it should check the ring being ready to use.

Bug: amdgpu_test crashes system on Tonga VF.

Signed-off-by: Ding Pixel <Pixel.Ding@xxxxxxx>
Reviewed-by: Christian KÃnig <christian.koenig@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index 82dc8d20e28a..bfb4b91869e7 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -83,6 +83,13 @@ int amdgpu_cs_get_ring(struct amdgpu_device *adev, u32 ip_type,
 		}
 		break;
 	}
+
+	if (!(*out_ring && (*out_ring)->adev)) {
+		DRM_ERROR("Ring %d is not initialized on IP %d\n",
+			  ring, ip_type);
+		return -EINVAL;
+	}
+
 	return 0;
 }
 
-- 
2.11.0