VCN_INFO_TABLE_MAX_NUM_INSTANCES vs AMDGPU_MAX_VCN_INSTANCES

[Ernst Sjöstrand]

Den mån 16 maj 2022 kl 17:13 skrev Alex Deucher <alexdeucher at gmail.com>:

> 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
>

It would be nice to get rid of this pattern and make sure it doesn't happen
again when the VCN info table is raised to 5.
It's very similar to the HWIP_MAX_INSTANCE issue.

//E
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