[Intel-gfx] [RFC PATCH] drm/i915: make context status notifier head be per engine

[Du, Changbin]

hi, is there any comments for this? I'd like hear chris and daniel's
comments. :)

Thanks,
Changbin

On Thu, Mar 02, 2017 at 07:23:05PM +0800, changbin.du at intel.com wrote:
> From: Changbin Du <changbin.du at intel.com>
> 
> hi, Daniel, Chris and All,
> As you know, GVTg introduced the context status notifier to schedule
> the GVTg workload. At that time, the notifier is bound to GVTg context
> only, so GVTg is not aware of host workloads.
> 
> Now we are going to improve GVTg's guest workload scheduler policy,
> and add Guc emulation support for new Gen graphics. Both these two
> features require acknowledgment for all contexts running on hardware.
> (But will not alter host workload.) So here try to make some change.
> 
> The change is easy:
>   1. Move the context status notifier head from i915_gem_context to
>      intel_engine_cs. Which means there is a notifier head per engine
>      instead of per context. Execlist driver still call notifier for
>      each context sched-in/out events of current engine.
>   2. At GVTg side, it binds a notifier_block for each physical engine
>      at GVTg initialization period. Then GVTg can hear all context
>      status events.
> 
> In this RFC patch, GVTg do nothing for host context event, but later
> will add a function there. But in any case, the notifier callback is
> a noop if this is no active vGPU.
> 
> Since intel_gvt_init() is called at early initialization stage and
> require the status notifier head has been initiated, I initiate it in
> intel_engine_setup(). I am not sure if this is the right place, please
> correct me if wrong. Thank you! Look forward to your feedback. :)
> 
> Signed-off-by: Changbin Du <changbin.du at intel.com>
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