VCN_INFO_TABLE_MAX_NUM_INSTANCES vs AMDGPU_MAX_VCN_INSTANCES

[Alex Deucher]

On Sun, May 15, 2022 at 11:46 AM Ernst Sjöstrand <ernstp at gmail.com> wrote:
>
> smatch found this problem on amd-staging-drm-next:
>
> drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c:1443 amdgpu_discovery_get_vcn_info() error: buffer overflow 'adev->vcn.vcn_codec_disable_mask' 2 <= 3
>
> This is caused by:
> #define AMDGPU_MAX_VCN_INSTANCES 2
> #define VCN_INFO_TABLE_MAX_NUM_INSTANCES 4
>
> Can we just drop VCN_INFO_TABLE_MAX_NUM_INSTANCES completely and use AMDGPU_MAX_VCN_INSTANCES everywhere instead (and bump it to 4)?

We should be able to bump AMDGPU_MAX_VCN_INSTANCES to 4 (although it
would waste some memory in the places it is used at this point).
VCN_INFO_TABLE_MAX_NUM_INSTANCES is part of a firmware structure so we
can't change that without breaking the firmware structure.

Alex


>
> //E
>