[Intel-gfx] [PATCH] drm/i915: Disable stolen memory when DMAR is active

[Daniel Vetter]

On Fri, Feb 28, 2014 at 12:14:02PM +0000, Chris Wilson wrote:
> We have reports of heavy screen corruption if we try to use the stolen
> memory reserved by the BIOS whilst the DMA-Remapper is active. This
> quirk may be only specific to a few machines or BIOSes, but first lets
> apply the big hammer and always disable use of stolen memory when DMAR
> is active.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=68535
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> ---
>  drivers/gpu/drm/i915/i915_gem_stolen.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
> index 984ada1b0084..13a849afe479 100644
> --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
> +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
> @@ -325,11 +325,25 @@ void i915_gem_cleanup_stolen(struct drm_device *dev)
>  	drm_mm_takedown(&dev_priv->mm.stolen);
>  }
>  
> +static bool need_dmar_wa(struct drm_device *dev)
> +{
> +#ifdef CONFIG_INTEL_IOMMU
> +	if (INTEL_INFO(dev)->gen >= 6 && intel_iommu_gfx_mapped)

Why the gen check in here? Without that we could just check
intel_iommu_gfx_mapped and shovel the #ifdef into stolen init. No need to
spread it out like that imo.
-Daniel

> +		return true;
> +#endif
> +	return false;
> +}
> +
>  int i915_gem_init_stolen(struct drm_device *dev)
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	struct resource *r;
>  
> +	if (need_dmar_wa(dev)) {
> +		DRM_INFO("DMAR active, disabling use of stolen memory\n");
> +		return 0;
> +	}
> +
>  	if (dev_priv->gtt.stolen_size == 0)
>  		return 0;
>  
> -- 
> 1.9.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch