[PATCH] drm/amd/powerplay: Protect backend resource when unload driver

[Christian König]

Am 27.09.19 um 12:07 schrieb Jesse Zhang:
> From: root <root at debian.debian>
>
> Guest driver can be unloaded while engines still using some
> backend resources. That would lead to use after free and then
> cause guest driver failed.
>
> Need to add mutex lock before backend resources free to make
> sure nobody is using it.
>
> Need to check backend data availablility before VCE/UVD enter
> powergating mode, if backend resources have been free, then
> skip entering powergating.
>
> Change-Id: If7f93221ddecc578884dc9e99a52f22a43e16b07
> Signed-off-by: Jesse Zhang <zhexi.zhang at amd.com>
> ---
>   drivers/gpu/drm/amd/powerplay/hwmgr/vega10_hwmgr.c | 14 ++++++++++----
>   1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/vega10_hwmgr.c b/drivers/gpu/drm/amd/powerplay/hwmgr/vega10_hwmgr.c
> index d08493b..a9320a5 100644
> --- a/drivers/gpu/drm/amd/powerplay/hwmgr/vega10_hwmgr.c
> +++ b/drivers/gpu/drm/amd/powerplay/hwmgr/vega10_hwmgr.c
> @@ -810,8 +810,10 @@ static int vega10_hwmgr_backend_fini(struct pp_hwmgr *hwmgr)
>   	kfree(hwmgr->dyn_state.vddc_dep_on_dal_pwrl);
>   	hwmgr->dyn_state.vddc_dep_on_dal_pwrl = NULL;
>   
> +	mutex_lock(&hwmgr->smu_lock);
>   	kfree(hwmgr->backend);
>   	hwmgr->backend = NULL;
> +	mutex_unlock(&hwmgr->smu_lock);
>   
>   	return 0;
>   }
> @@ -4619,16 +4621,20 @@ static void vega10_power_gate_vce(struct pp_hwmgr *hwmgr, bool bgate)
>   {
>   	struct vega10_hwmgr *data = hwmgr->backend;

Is the mutex locked by the caller here?

>   
> -	data->vce_power_gated = bgate;
> -	vega10_enable_disable_vce_dpm(hwmgr, !bgate);
> +	if(data){

Missing spaces and it is usually better to do this like:

if (!data)
     return;

Since this is essentially error handling.

Regards,
Christian.

> +		data->vce_power_gated = bgate;
> +		vega10_enable_disable_vce_dpm(hwmgr, !bgate);
> +	}
>   }
>   
>   static void vega10_power_gate_uvd(struct pp_hwmgr *hwmgr, bool bgate)
>   {
>   	struct vega10_hwmgr *data = hwmgr->backend;
>   
> -	data->uvd_power_gated = bgate;
> -	vega10_enable_disable_uvd_dpm(hwmgr, !bgate);
> +	if(data){
> +		data->uvd_power_gated = bgate;
> +		vega10_enable_disable_uvd_dpm(hwmgr, !bgate);
> +	}
>   }
>   
>   static inline bool vega10_are_power_levels_equal(