Re: [PATCH] drm/i915/cmdparser: Limit clflush to active cachelines

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> We only need to clflush those cachelines that we have validated to be
> read by the GPU. Userspace typically fills the batch length in
> correctly, the exceptions tend to be explicit tests within igt.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_cmd_parser.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c
> index 21b1cd917d81..b9ce9a6881ea 100644
> --- a/drivers/gpu/drm/i915/i915_cmd_parser.c
> +++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
> @@ -1331,7 +1331,8 @@ int intel_engine_cmd_parser(struct intel_engine_cs *engine,
>  	}
>  
>  	if (ret == 0 && needs_clflush_after)
> -		drm_clflush_virt_range(shadow_batch_obj->mm.mapping, batch_len);
> +		drm_clflush_virt_range(shadow_batch_obj->mm.mapping,
> +				       (void *)cmd - shadow_batch_obj->mm.mapping);

(void *)cmd - ptr_mask_bit(shadow_batch_obj->mm.mapping)

We get away as the wb mapping being zero but for correctness.

-Mika

>  	i915_gem_object_unpin_map(shadow_batch_obj);
>  
>  	return ret;
> -- 
> 2.11.0
>
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