[Intel-gfx] [PATCH 7/9] drm/i915: Introduce execlist context status change notification

[Chris Wilson]

On Tue, May 17, 2016 at 04:19:07AM -0400, Zhi Wang wrote:
> This patch introduces an approach to track the execlist context status
> change.
> 
> GVT-g uses GVT context as the "shadow context". The content inside GVT
> context will be copied back to guest after the context is idle. So GVT-g
> has to know the status of the execlist context.
> 
> This function is configurable in the context creation service. Currently,
> Only GVT-g will create the "status-change-notification" enabled GEM
> context.
> 
> v5:
> 
> - Only compile this feature when CONFIG_DRM_I915_GVT is enabled.(Tvrtko)
> 
> Signed-off-by: Zhi Wang <zhi.a.wang at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h  |  6 ++++++
>  drivers/gpu/drm/i915/intel_lrc.c | 30 ++++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_lrc.h |  7 +++++++
>  3 files changed, 43 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 91f69e5..9688006 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -882,9 +882,15 @@ struct intel_context {
>  		u64 lrc_desc;
>  		uint32_t *lrc_reg_state;
>  		bool initialised;
> +#if IS_ENABLED(CONFIG_DRM_I915_GVT)
> +		struct atomic_notifier_head status_notifier_head;

struct atomic_notifier_head status_notifier;

> +#endif
>  	} engine[I915_NUM_ENGINES];
>  	u32 ring_buffer_size;
>  	bool use_48bit_addressing_mode;
> +#if IS_ENABLED(CONFIG_DRM_I915_GVT)
> +	bool enable_status_change_notification;

unsigned status_notify;

> +#endif
>  
>  	struct list_head link;
>  };
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index d97623f..9069836 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -415,6 +415,20 @@ static void execlists_submit_requests(struct drm_i915_gem_request *rq0,
>  	spin_unlock_irq(&dev_priv->uncore.lock);
>  }
>  
> +#if IS_ENABLED(CONFIG_DRM_I915_GVT)

Actually, I think there will be other use cases for this notifier.
So let's not clutter the code with #ifdefs. Remove the ones from the
struct and do

> +static inline void execlists_context_status_change(
> +		struct drm_i915_gem_request *req,
> +		unsigned long status)
> +{

	if (!IS_ENABLED(CONFIG_DRM_I915_GVT))
		return;

instead. The compiler should be fine with the dead-code elimination.


> +	if (!req->ctx->enable_status_change_notification)

What locks are you holding here?

if (!READ_ONCE(req->ctx->status_notify))
	return;

> +		return;
> +
> +	atomic_notifier_call_chain(
> +			&req->ctx->engine[req->engine->id].status_notifier_head,

I think we have enough justification for req->ctx_engine;

> +			status, req);
> +}
> +#endif
> +
>  static void execlists_context_unqueue(struct intel_engine_cs *engine)
>  {
>  	struct drm_i915_gem_request *req0 = NULL, *req1 = NULL;
> @@ -450,6 +464,13 @@ static void execlists_context_unqueue(struct intel_engine_cs *engine)
>  	if (unlikely(!req0))
>  		return;
>  
> +#if IS_ENABLED(CONFIG_DRM_I915_GVT)
> +	execlists_context_status_change(req0, CONTEXT_SCHEDULE_IN);
> +
> +	if (req1)
> +		execlists_context_status_change(req1, CONTEXT_SCHEDULE_IN);

> +#endif
> +
>  	if (req0->elsp_submitted & engine->idle_lite_restore_wa) {
>  		/*
>  		 * WaIdleLiteRestore: make sure we never cause a lite restore
> @@ -488,6 +509,10 @@ execlists_check_remove_request(struct intel_engine_cs *engine, u32 ctx_id)
>  	if (--head_req->elsp_submitted > 0)
>  		return 0;
>  
> +#if IS_ENABLED(CONFIG_DRM_I915_GVT)
> +	execlists_context_status_change(head_req, CONTEXT_SCHEDULE_OUT);
> +#endif
> +
>  	list_del(&head_req->execlist_link);
>  	i915_gem_request_unreference(head_req);
>  
> @@ -2534,6 +2559,11 @@ static int execlists_context_deferred_alloc(struct intel_context *ctx,
>  	ctx->engine[engine->id].state = ctx_obj;
>  	ctx->engine[engine->id].initialised = engine->init_context == NULL;
>  
> +#if IS_ENABLED(CONFIG_DRM_I915_GVT)
> +	if (ctx->enable_status_change_notification)

Always do the init. That allows us to start switching the notify on/off
at runtime.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre