[Intel-gfx] [PATCH] drm/i915: Add missed MI_BATCH_BUFFER_END in null state batch buffer.

[Mika Kuoppala]

Zhi Wang <zhi.a.wang at intel.com> writes:

> Currently MI_BATCH_BUFFER_END is missed in null state batch buffer.
> This fix is trying to append the missed instruction at the end of
> null state batch buffer gem bo after it was initialized and filled
> with null state commands.
>
> This issue was exposed under full GPU virtualization(Intel GVT-g) environment.
>
> Signed-off-by: Zhi Wang <zhi.a.wang at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem_render_state.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_render_state.c b/drivers/gpu/drm/i915/i915_gem_render_state.c
> index 98dcd94..3495b4b 100644
> --- a/drivers/gpu/drm/i915/i915_gem_render_state.c
> +++ b/drivers/gpu/drm/i915/i915_gem_render_state.c
> @@ -54,7 +54,8 @@ static int render_state_init(struct render_state *so, struct drm_device *dev)
>  	if (so->rodata == NULL)
>  		return 0;
>  
> -	if (so->rodata->batch_items * 4 > 4096)
> +	/* Leave one dword for MI_BATCH_BUFFER_END. */
> +	if ((so->rodata->batch_items * 4 + 1) > 4096)
>  		return -EINVAL;
>  
>  	so->obj = i915_gem_alloc_object(dev, 4096);
> @@ -108,6 +109,7 @@ static int render_state_setup(struct render_state *so)
>  
>  		d[i++] = s;
>  	}
> +	d[i] = MI_BATCH_BUFFER_END;
>  	kunmap(page);
>

The states themselves have the end explicitly. In i-g-t:

intel-gpu-tools/tools/null_state_gen (master)$ grep BUFFER_END *.c
intel_renderstate_gen6.c:       OUT_BATCH(MI_BATCH_BUFFER_END);
intel_renderstate_gen7.c:       OUT_BATCH(MI_BATCH_BUFFER_END);
intel_renderstate_gen8.c:       OUT_BATCH(MI_BATCH_BUFFER_END);
intel_renderstate_gen9.c:       OUT_BATCH(MI_BATCH_BUFFER_END);

Please check that your state generator emits it correctly.
-Mika

>  	ret = i915_gem_object_set_to_gtt_domain(so->obj, false);
> -- 
> 1.8.3.2
>
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