Re: [PATCH] drm/i915: Detect invalid pages for SandyBridge

From: Daniel Vetter <daniel@ffwll.ch>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] drm/i915: Detect invalid pages for SandyBridge
Date: Thu, 27 Sep 2012 14:16:11 +0200	[thread overview]
Message-ID: <20120927121611.GD2098@bremse> (raw)
In-Reply-To: <20120927121422.GC2098@bremse>

On Thu, Sep 27, 2012 at 02:14:22PM +0200, Daniel Vetter wrote:
> On Thu, Sep 27, 2012 at 09:27:57AM +0100, Chris Wilson wrote:
> > As SandyBridge returns garbage when decoding certain addresses through
> > the GTT (all memory below 1MiB and a very small number of individual
> > pages) we need to prevent the GPU from utilizing those pages. The
> > ultimate goal would be to prevent our allocator from handing us those
> > pages, but that is a longer term project. In the short term, we can
> > detect when we attempt to bind those pages to the GPU and return an
> > error to the application rather than hang the GPU and potentially the
> > system.
> > 
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > ---
> >  drivers/gpu/drm/i915/i915_gem_gtt.c |   40 ++++++++++++++++++++++++++++++++---
> >  1 file changed, 37 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > index d9d3fc7..5c7ccfd 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > @@ -306,17 +306,51 @@ void i915_gem_restore_gtt_mappings(struct drm_device *dev)
> >  	intel_gtt_chipset_flush();
> >  }
> >  
> > +static bool
> > +gen6_valid_addresses(struct drm_i915_gem_object *obj)
> > +{
> > +	struct scatterlist *sg;
> > +	int i;
> > +
> > +	for_each_sg(obj->pages->sgl, sg, obj->pages->nents, i) {
> > +		dma_addr_t addr = sg_dma_address(sg);
> > +		if (WARN(addr < 0x100000 ||
> > +			 addr == 0x20050000 ||
> > +			 addr == 0x20110000 ||
> > +			 addr == 0x20130000 ||
> > +			 addr == 0x20138000 ||
> > +			 addr == 0x40004000,
> > +			 "object references unaddressable physical pages: addr=%x",
> > +			 (u32)addr))
> > +			return false;
> 
> Iirc the bug is about the physical address, no the remapped one after
> dmar. We'd need to check the windows code for that though ...

Also maybe don't fail, but only smash some dirt into dmesg - otherwise
we'll score a neat regression report and probably angry users.
-Daniel

> 
> > +	}
> > +
> > +	return true;
> > +}
> > +
> >  int i915_gem_gtt_prepare_object(struct drm_i915_gem_object *obj)
> >  {
> > -	if (obj->has_dma_mapping)
> > -		return 0;
> > +	int ret;
> >  
> > -	if (!dma_map_sg(&obj->base.dev->pdev->dev,
> > +	if (!obj->has_dma_mapping &&
> > +	    !dma_map_sg(&obj->base.dev->pdev->dev,
> >  			obj->pages->sgl, obj->pages->nents,
> >  			PCI_DMA_BIDIRECTIONAL))
> >  		return -ENOSPC;
> >  
> > +	if (IS_GEN6(obj->base.dev) && !gen6_valid_addresses(obj)) {
> > +		ret = -EFAULT;
> > +		goto unmap;
> > +	}
> > +
> >  	return 0;
> > +
> > +unmap:
> > +	if (!obj->has_dma_mapping)
> > +		dma_unmap_sg(&obj->base.dev->pdev->dev,
> > +			     obj->pages->sgl, obj->pages->nents,
> > +			     PCI_DMA_BIDIRECTIONAL);
> > +	return ret;
> >  }
> >  
> >  void i915_gem_gtt_bind_object(struct drm_i915_gem_object *obj,
> > -- 
> > 1.7.10.4
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch

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