Re: [PATCH] drm/i915: Sanitize the enable_ppgtt module option once

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 24 Apr 2014, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> On Wed, 23 Apr 2014, Daniel Vetter <daniel@ffwll.ch> wrote:
>> On Wed, Apr 23, 2014 at 11:37:46AM +0300, Jani Nikula wrote:
>>> On Tue, 22 Apr 2014, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>>> > Otherwise we'll end up spamming dmesg on every context creation on snb
>>> > with vt-d enabled. This regression was introduced in
>>> >
>>> > commit 246cbfb5fb9a1ca0997fbb135464c1ff5bb9c549
>>> > Author: Ben Widawsky <benjamin.widawsky@intel.com>
>>> > Date:   Fri Dec 6 14:11:14 2013 -0800
>>> >
>>> >     drm/i915: Reorganize intel_enable_ppgtt
>>> >
>>> > References: https://lkml.org/lkml/2014/4/17/599
>>> > Cc: Alessandro Suardi <alessandro.suardi@gmail.com>
>>> > Cc: Ben Widawsky <ben@bwidawsk.net>
>>> > Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>>> > ---
>>> >  drivers/gpu/drm/i915/i915_gem_gtt.c | 26 +++++++++++++++++++-------
>>> >  1 file changed, 19 insertions(+), 7 deletions(-)
>>> >
>>> > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
>>> > index 0d514ff9b94c..47491c4a1181 100644
>>> > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
>>> > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
>>> > @@ -34,25 +34,35 @@ static void gen8_setup_private_ppat(struct drm_i915_private *dev_priv);
>>> >  
>>> >  bool intel_enable_ppgtt(struct drm_device *dev, bool full)
>>> >  {
>>> > -	if (i915.enable_ppgtt == 0 || !HAS_ALIASING_PPGTT(dev))
>>> > +	if (i915.enable_ppgtt == 0)
>>> >  		return false;
>>> >  
>>> >  	if (i915.enable_ppgtt == 1 && full)
>>> >  		return false;
>>> >  
>>> > +	return true;
>>> > +}
>>> > +
>>> > +static int sanitize_enable_ppgtt(struct drm_device *dev, int enable_ppgtt)
>>> > +{
>>> > +	if (enable_ppgtt == 0 || !HAS_ALIASING_PPGTT(dev))
>>> > +		return 0;
>>> > +
>>> > +	if (i915.enable_ppgtt == 1)
>>> > +		return 1;
>>> > +
>>> > +	if (i915.enable_ppgtt == 2 && HAS_PPGTT(dev))
>>> > +		return 2;
>>> 
>>> You should probably either pass enable_ppgtt as parameter and use that
>>> exclusively, or not pass it and refer to i915.enable_ppgtt directly, but
>>> not mix them.
>>
>> New patch on its way with Chris' comments also applied.
>>> 
>>> > +
>>> >  #ifdef CONFIG_INTEL_IOMMU
>>> >  	/* Disable ppgtt on SNB if VT-d is on. */
>>> >  	if (INTEL_INFO(dev)->gen == 6 && intel_iommu_gfx_mapped) {
>>> >  		DRM_INFO("Disabling PPGTT because VT-d is on\n");
>>> > -		return false;
>>> > +		return 0;
>>> >  	}
>>> >  #endif
>>> >  
>>> > -	/* Full ppgtt disabled by default for now due to issues. */
>>> > -	if (full)
>>> > -		return HAS_PPGTT(dev) && (i915.enable_ppgtt == 2);
>>> > -	else
>>> > -		return HAS_ALIASING_PPGTT(dev);
>>> > +	return HAS_ALIASING_PPGTT(dev) ? 1 : 0;
>>> 
>>> 
>>> This conflicts in -fixes due to
>>> commit 8d214b7d9c45f4af23ce41b2bc74f79c44f760de
>>> Author: Ben Widawsky <benjamin.widawsky@linux.intel.com>
>>> Date:   Mon Mar 24 18:06:00 2014 -0700
>>> 
>>>     drm/i915: Allow full PPGTT with param override
>>> 
>>> Should I incorporate that in the conflict resolution for simplicity,
>>> letting 3.15 users also play with full ppgtt with the module param?
>>
>> Yeah I guess it's easiest to just cherry-pick that one to -fixes, too.
>> -Daniel
>
> Pushed v2 to -fixes, along with "drm/i915: Allow full PPGTT with param
> override". Thanks for the patch and review.

And yanked out again due to [1]. Back to the drawing board. Please also
add a ppgtt sanity check BUG_ON before returning true from
intel_enable_ppgtt().

BR,
Jani.


[1] https://bugs.freedesktop.org/show_bug.cgi?id=77916

-- 
Jani Nikula, Intel Open Source Technology Center