Re: [PATCH 2/4] drm/i915/guc: Cancel requests immediately

John Harrison
2022-01-26T18:59:08Z

On 1/24/2022 07:01, Matthew Brost wrote:
> Change the preemption timeout to the smallest possible value (1 us) when
> disabling scheduling to cancel a request and restore it after
> cancellation. This not only cancels the request as fast as possible, it
> fixes a bug where the preemption timeout is 0 which results in the
> schedule disable hanging forever.
Shouldn't there be an 'if' in the above statement? The pre-emption
timeout is not normally zero.

>
> Reported-by: Jani Saarinen <jani.saarinen@intel.com>
> Fixes: 62eaf0ae217d4 ("drm/i915/guc: Support request cancellation")
> Link: https://gitlab.freedesktop.org/drm/intel/-/issues/4960
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
> drivers/gpu/drm/i915/gt/intel_context_types.h | 5 ++
> .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 46 +++++++++++--------
> 2 files changed, 31 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
> index 30cd81ad8911a..730998823dbea 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
> @@ -198,6 +198,11 @@ struct intel_context {
> * each priority bucket
> */
> u32 prio_count[GUC_CLIENT_PRIORITY_NUM];
> + /**
> + * @preemption_timeout: preemption timeout of the context, used
> + * to restore this value after request cancellation
> + */
> + u32 preemption_timeout;
> } guc_state;
>
> struct {
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> index 3918f1be114fa..966947c450253 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -2147,7 +2147,8 @@ static inline u32 get_children_join_value(struct intel_context *ce,
> return __get_parent_scratch(ce)->join[child_index].semaphore;
> }
>
> -static void guc_context_policy_init(struct intel_engine_cs *engine,
> +static void guc_context_policy_init(struct intel_context *ce,
> + struct intel_engine_cs *engine,
> struct guc_lrc_desc *desc)
Shouldn't engine be before ce? The more general structure usually goes
first.

John.

> {
> desc->policy_flags = 0;
> @@ -2157,7 +2158,8 @@ static void guc_context_policy_init(struct intel_engine_cs *engine,
>
> /* NB: For both of these, zero means disabled. */
> desc->execution_quantum = engine->props.timeslice_duration_ms * 1000;
> - desc->preemption_timeout = engine->props.preempt_timeout_ms * 1000;
> + ce->guc_state.preemption_timeout = engine->props.preempt_timeout_ms * 1000;
> + desc->preemption_timeout = ce->guc_state.preemption_timeout;
> }
>
> static int guc_lrc_desc_pin(struct intel_context *ce, bool loop)
> @@ -2193,7 +2195,7 @@ static int guc_lrc_desc_pin(struct intel_context *ce, bool loop)
> desc->hw_context_desc = ce->lrc.lrca;
> desc->priority = ce->guc_state.prio;
> desc->context_flags = CONTEXT_REGISTRATION_FLAG_KMD;
> - guc_context_policy_init(engine, desc);
> + guc_context_policy_init(ce, engine, desc);
>
> /*
> * If context is a parent, we need to register a process descriptor
> @@ -2226,7 +2228,7 @@ static int guc_lrc_desc_pin(struct intel_context *ce, bool loop)
> desc->hw_context_desc = child->lrc.lrca;
> desc->priority = ce->guc_state.prio;
> desc->context_flags = CONTEXT_REGISTRATION_FLAG_KMD;
> - guc_context_policy_init(engine, desc);
> + guc_context_policy_init(child, engine, desc);
> }
>
> clear_children_join_go_memory(ce);
> @@ -2409,6 +2411,19 @@ static u16 prep_context_pending_disable(struct intel_context *ce)
> return ce->guc_id.id;
> }
>
> +static void __guc_context_set_preemption_timeout(struct intel_guc *guc,
> + u16 guc_id,
> + u32 preemption_timeout)
> +{
> + u32 action[] = {
> + INTEL_GUC_ACTION_SET_CONTEXT_PREEMPTION_TIMEOUT,
> + guc_id,
> + preemption_timeout
> + };
> +
> + intel_guc_send_busy_loop(guc, action, ARRAY_SIZE(action), 0, true);
> +}
> +
> static struct i915_sw_fence *guc_context_block(struct intel_context *ce)
> {
> struct intel_guc *guc = ce_to_guc(ce);
> @@ -2442,8 +2457,10 @@ static struct i915_sw_fence *guc_context_block(struct intel_context *ce)
>
> spin_unlock_irqrestore(&ce->guc_state.lock, flags);
>
> - with_intel_runtime_pm(runtime_pm, wakeref)
> + with_intel_runtime_pm(runtime_pm, wakeref) {
> + __guc_context_set_preemption_timeout(guc, guc_id, 1);
> __guc_context_sched_disable(guc, ce, guc_id);
> + }
>
> return &ce->guc_state.blocked;
> }
> @@ -2492,8 +2509,10 @@ static void guc_context_unblock(struct intel_context *ce)
>
> spin_unlock_irqrestore(&ce->guc_state.lock, flags);
>
> - if (enable) {
> - with_intel_runtime_pm(runtime_pm, wakeref)
> + with_intel_runtime_pm(runtime_pm, wakeref) {
> + __guc_context_set_preemption_timeout(guc, ce->guc_id.id,
> + ce->guc_state.preemption_timeout);
> + if (enable)
> __guc_context_sched_enable(guc, ce);
> }
> }
> @@ -2521,19 +2540,6 @@ static void guc_context_cancel_request(struct intel_context *ce,
> }
> }
>
> -static void __guc_context_set_preemption_timeout(struct intel_guc *guc,
> - u16 guc_id,
> - u32 preemption_timeout)
> -{
> - u32 action[] = {
> - INTEL_GUC_ACTION_SET_CONTEXT_PREEMPTION_TIMEOUT,
> - guc_id,
> - preemption_timeout
> - };
> -
> - intel_guc_send_busy_loop(guc, action, ARRAY_SIZE(action), 0, true);
> -}
> -
> static void guc_context_ban(struct intel_context *ce, struct i915_request *rq)
> {
> struct intel_guc *guc = ce_to_guc(ce);