Re: [PATCH v3] drm/i915: limit PPGTT size to 2GB in 32-bit platforms

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, May 29, 2015 at 02:15:05PM +0100, Michel Thierry wrote:
> We already set this limit for the GGTT.
> 
> This is a temporary patch until a full replacement of size_t variables
> (inadequate in 32-bit kernel) is in place.
> 
> Regression from:
> 	commit a4e0bedca678c81eea4cd79a4bd502335639f73a
> 	Author: Michel Thierry <michel.thierry@intel.com>
> 	Date:   Wed Apr 8 12:13:35 2015 +0100
> 
> 		drm/i915: Use complete address space in true PPGTT
> 
> v2: Prettify code and explain why this is needed. (Chris)
> v3: Don't hide the compilation warning in 32-bit. (Chris)
> 
> Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Michel Thierry <michel.thierry@intel.com>

Queued for -next, thanks for the patch.
-Daniel

> ---
>  drivers/gpu/drm/i915/i915_gem_gtt.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index 17b7df0..619dad1 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -952,6 +952,13 @@ static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
>  
>  	ppgtt->base.start = 0;
>  	ppgtt->base.total = 1ULL << 32;
> +	if (IS_ENABLED(CONFIG_X86_32))
> +		/* While we have a proliferation of size_t variables
> +		 * we cannot represent the full ppgtt size on 32bit,
> +		 * so limit it to the same size as the GGTT (currently
> +		 * 2GiB).
> +		 */
> +		ppgtt->base.total = to_i915(ppgtt->base.dev)->gtt.base.total;
>  	ppgtt->base.cleanup = gen8_ppgtt_cleanup;
>  	ppgtt->base.allocate_va_range = gen8_alloc_va_range;
>  	ppgtt->base.insert_entries = gen8_ppgtt_insert_entries;
> -- 
> 2.4.0
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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