[Intel-gfx] [PATCH] drm/i915: set initialised only when init_context callback is NULL

[Chris Wilson]

On Thu, May 11, 2017 at 06:07:42PM +0800, Chuanxiao Dong wrote:
> initialised is fixup by the GVT shadow context as true to avoid the init
> from the host because it cannot take the settings from the host. Add a
> check to let host driver only overwrite it when the init callback is NULL

During execlist_context_deferred_alloc() we presumed that the context is
uninitialised (we only just allocated the state object for it!) and
chose to optimise away the later call to engine->init_context() if
engine->init_context were NULL. This breaks with GVT's contexts that are
marked as pre-initialised to avoid us annoyingly calling 
engine->init_context(). The fix is to not override ce->initialised if it
is already true.

> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Chuanxiao Dong <chuanxiao.dong at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_lrc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 319d9a8..d0e9b61 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -1956,7 +1956,8 @@ static int execlists_context_deferred_alloc(struct i915_gem_context *ctx,
>  
>  	ce->ring = ring;
>  	ce->state = vma;
> -	ce->initialised = engine->init_context == NULL;
> +	if (!engine->init_context)
> +		ce->initialised = true;

Does the compiler generate a cmov?
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre