[Intel-gfx] [PATCH] drm/i915: Ironlake GPU with VT-d fix

[Ben Widawsky]

On Thu, 22 Sep 2011 21:50:49 -0700
Keith Packard <keithp at keithp.com> wrote:

> On Thu, 22 Sep 2011 17:11:52 -0700, Ben Widawsky <ben at bwidawsk.net>
> wrote:
> 
> > It requires an additional IOMMU patch.
> 
> Can we collect those two patches into one sequence?
> 

Yes. Although not sure who would do the pull request to Linus.

> > +	if ((gpu_devid == PCI_DEVICE_ID_INTEL_IRONLAKE_M_HB ||
> > +	     gpu_devid == PCI_DEVICE_ID_INTEL_IRONLAKE_M_IG) &&
> > +	     intel_private.base.needs_dmar)
> > +		intel_private.base.do_idle_maps = 1;
> > +
> 
> I'd like to make this conditional on whether IOMMU is actually in use;
> needs_dmar is based solely on whether the DMA_API is compiled into the
> kernel and the GTT gen is > 2.

David did mention a way for me to detect it. I wasn't sure if there was a
deadline to get this patch out so I submitted it now. I will work on the
detection portion of it while the rest gets review. It's something like, check
if the bus address == the physical address and if not, assume the IOMMU is in
use.

> 
> > -	if (lists_empty)
> > +	if (lists_empty && !!dev_priv->mm.gtt->do_idle_maps)
> >  		return 0;
> 
> Is it necessary to change the semantic of this function in cases which
> aren't related to GTT remapping? Seems like you're imposing a fairly
> high cost on operations which don't actually need it.
> 

Not sure I follow. On that specific hunk it's apparently needed. I tried the
patch without this and we got some data back which suggested it didn't work. It
would be nice if we could reproduce this locally...

Ben