A compute shader dispatch encodes its workgroup counts in the CFG0..CFG2 registers. Kicking off a dispatch with a zero count in any of the three dimensions is invalid. First, the hardware will process 0 as 65536, while the user-space driver exposes a maximum of 65535. Over that, a submission with a zeroed workgroup dimension should be a no-op.
These zeroed counts can reach the dispatch path through an indirect CSD job, whose workgroup counts are only known once the indirect buffer is read and may legitimately be zero, but such scenario should only result in a no-op. Don't submit the job to the hardware when any of the workgroup counts is zero, so the job completes immediately instead of running the shader. Cc: [email protected] Fixes: d223f98f0209 ("drm/v3d: Add support for compute shader dispatch.") Suggested-by: Jose Maria Casanova Crespo <[email protected]> Signed-off-by: Maíra Canal <[email protected]> Reviewed-by: Iago Toral Quiroga <[email protected]> --- drivers/gpu/drm/v3d/v3d_sched.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/gpu/drm/v3d/v3d_sched.c b/drivers/gpu/drm/v3d/v3d_sched.c index 47f83936cd73..6678d62e5bd0 100644 --- a/drivers/gpu/drm/v3d/v3d_sched.c +++ b/drivers/gpu/drm/v3d/v3d_sched.c @@ -352,6 +352,16 @@ v3d_csd_job_run(struct drm_sched_job *sched_job) return NULL; } + /* The HW interprets a workgroup size of 0 as 65536; however, the + * user-space driver exposes a maximum of 65535. Therefore, a 0 in + * any dimension means that we have no workgroups and the compute + * shader should not be dispatched. + */ + if (!V3D_GET_FIELD(job->args.cfg[0], V3D_CSD_QUEUED_CFG0_NUM_WGS_X) || + !V3D_GET_FIELD(job->args.cfg[1], V3D_CSD_QUEUED_CFG1_NUM_WGS_Y) || + !V3D_GET_FIELD(job->args.cfg[2], V3D_CSD_QUEUED_CFG2_NUM_WGS_Z)) + return NULL; + v3d->queue[V3D_CSD].active_job = &job->base; v3d_invalidate_caches(v3d); -- 2.54.0
