[Intel-gfx] [PATCH 11/16] drm/i915/execlists: Request the kernel context be pinned high

[Tvrtko Ursulin]

On 07/12/2016 13:58, Chris Wilson wrote:
> PIN_HIGH is an expensive operation (in comparison to allocating from the
> hole stack) unsuitable for frequent use (such as switching between
> contexts). However, the kernel context should be pinned just once for
> the lifetime of the driver, and here it is appropriate to keep it out of
> the mappable range (in order to maximise mappable space for users).
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/intel_lrc.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 58cea1f9ad27..22ded92d0346 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -767,6 +767,7 @@ static int execlists_context_pin(struct intel_engine_cs *engine,
>  				 struct i915_gem_context *ctx)
>  {
>  	struct intel_context *ce = &ctx->engine[engine->id];
> +	unsigned int flags;
>  	void *vaddr;
>  	int ret;
>
> @@ -781,8 +782,11 @@ static int execlists_context_pin(struct intel_engine_cs *engine,
>  			goto err;
>  	}
>
> -	ret = i915_vma_pin(ce->state, 0, GEN8_LR_CONTEXT_ALIGN,
> -			   PIN_OFFSET_BIAS | GUC_WOPCM_TOP | PIN_GLOBAL);
> +	flags = PIN_OFFSET_BIAS | GUC_WOPCM_TOP | PIN_GLOBAL;
> +	if (ctx == ctx->i915->kernel_context)
> +		flags |= PIN_HIGH;
> +
> +	ret = i915_vma_pin(ce->state, 0, GEN8_LR_CONTEXT_ALIGN, flags);
>  	if (ret)
>  		goto err;
>
>

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Regards,

Tvrtko