[Beignet] [PATCH] Fix AUX buffer for really page aligned

[Zhenyu Wang]

On 2014.10.22 08:49:53 +0000, Guo, Yejun wrote:
> three comments in line, thanks.
> 

Thanks for review this.

>    gpgpu->aux_offset.surface_heap_offset = size_aux;
>    size_aux += sizeof(surface_heap_t);
>  
> @@ -784,7 +782,10 @@ intel_gpgpu_state_init(intel_gpgpu_t *gpgpu,
>    gpgpu->aux_offset.sampler_border_color_state_offset = size_aux;
>    size_aux += GEN_MAX_SAMPLERS * sizeof(gen7_sampler_border_color_t);
> 
> [Yejun] aux buffer contains several parts, each part has its own alignment requirement, so we can see several 'ALIGN'  in above code. The alignment is handled for each part, it is not feasible to move one/all of them to the last.
> 

The goal is to make sure final aux buffer size is page aligned after
adding up all required aligned space size. My patch only counts on
final size.

>  
> -  bo = dri_bo_alloc(gpgpu->drv->bufmgr, "AUX_BUFFER", size_aux, 0);
> +  //surface heap must be 4096 bytes aligned because state base address 
> + use 20bit for the address  size_aux = ALIGN(size_aux, 4096);
> +
> +  bo = dri_bo_alloc(gpgpu->drv->bufmgr, "AUX_BUFFER", size_aux, 4096);
> 
> [Yejun] the last parameter '4096' is to control the size of the whole buffer (to be page aligned), not to meet the align requirement of the base address, and it is not explicitly required and  is ignored in function drm_intel_gem_bo_alloc_internal. 
> 

It's for 'alignment' parameter. Yes current libdrm will optimize it as to be
page aligned, but as your comment above it's a good note to say that we need
aux buffer allocation to be page aligned, like for other objects, printf buf,
timestamp, etc.

-- 
Open Source Technology Center, Intel ltd.

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