[PATCH 19/22] drm/amdgpu: Fix the warning division or modulo by zero for the variable num_xcc_per_xcp

[Zhang, Jesse(Jie)]

[AMD Official Use Only - General]

Hi Lijo,

-----Original Message-----
From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of Lazar, Lijo
Sent: Friday, May 10, 2024 3:16 PM
To: amd-gfx at lists.freedesktop.org
Subject: Re: [PATCH 19/22] drm/amdgpu: Fix the warning division or modulo by zero for the variable num_xcc_per_xcp



On 5/10/2024 8:20 AM, Jesse Zhang wrote:
> Dividing expression num_xcc_per_xcp which may be zero has undefined behavior.
>
> Signed-off-by: Jesse Zhang <Jesse.Zhang at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/aqua_vanjaram.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/aqua_vanjaram.c
> b/drivers/gpu/drm/amd/amdgpu/aqua_vanjaram.c
> index 414ea3f560a7..5752c6760992 100644
> --- a/drivers/gpu/drm/amd/amdgpu/aqua_vanjaram.c
> +++ b/drivers/gpu/drm/amd/amdgpu/aqua_vanjaram.c
> @@ -522,6 +522,9 @@ static int aqua_vanjaram_switch_partition_mode(struct amdgpu_xcp_mgr *xcp_mgr,
>               goto unlock;
>
>       num_xcc_per_xcp = __aqua_vanjaram_get_xcc_per_xcp(xcp_mgr, mode);
> +     if (!num_xcc_per_xcp)
> +             goto unlock;
> +

This won't happen as the mode is validated before and for each valid mode a non-zero num_xcc_per_xcp is expected. To satisfy the warning-checker, before going to unlock use a proper 'ret' value also (otherwise it will look odd).

[Zhang, Jesse(Jie)]  Is that possible?
When the initialization mode is AMDGPU_AUTO_COMPUTE_PARTITION_MODE,
and get AMDGPU_UNKNOWN_COMPUTE_PARTITION_MODE through __aqua_vanjaram_get_auto_mode.

If so, it will skip the valid mode function (__aqua_vanjaram_is_valid_mode).

Thanks
Jesse


Thanks,
Lijo

>       if (adev->gfx.funcs->switch_partition_mode)
>               adev->gfx.funcs->switch_partition_mode(xcp_mgr->adev,
>                                                      num_xcc_per_xcp);