Re: [PATCH] drm/i915: Initialize the aliasing ppgtt as part of global gtt

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Aug 06, 2014 at 08:18:52AM +0000, Thierry, Michel wrote:
> 
> 
> > -----Original Message-----
> > From: Daniel Vetter [mailto:daniel.vetter@ffwll.ch]
> > Sent: Monday, August 04, 2014 3:19 PM
> > To: Intel Graphics Development
> > Cc: Daniel Vetter; Thierry, Michel; Ville Syrjälä
> > Subject: [PATCH] drm/i915: Initialize the aliasing ppgtt as part of global gtt
> > 
> > Stuffing this into the context setup code doesn't make a lot of sense.
> > Also reusing the real ppgtt setup code makes even less sense since the
> > aliasing ppgtt isn't a real address space. Leaving all that stuff
> > unitialized will make sure that we catch any abusers promptly.
> > 
> > This is also a prep work to clean up the context->ppgtt link.
> > 
> > v2: Fix up the logic fail, I've fumbled it so badly to completely
> > disable ppgtt on gen6. Spotted by Ville and Michel. Also move around
> > the pde write into the gen6 init function, since otherwise it won't
> > work at all.
> > 
> > Cc: "Thierry, Michel" <michel.thierry@intel.com>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> > ---
> >  drivers/gpu/drm/i915/i915_gem_context.c | 13 +---------
> >  drivers/gpu/drm/i915/i915_gem_gtt.c     | 42 +++++++++++++++++++++++-
> > ---------
> >  2 files changed, 31 insertions(+), 24 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem_context.c
> > b/drivers/gpu/drm/i915/i915_gem_context.c
> > index 3b8367aa8404..7a455fcee3a7 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_context.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> > @@ -276,17 +276,6 @@ i915_gem_create_context(struct drm_device *dev,
> >  			goto err_unpin;
> >  		} else
> >  			ctx->vm = &ppgtt->base;
> > -
> > -		/* This case is reserved for the global default context and
> > -		 * should only happen once. */
> > -		if (is_global_default_ctx) {
> > -			if (WARN_ON(dev_priv->mm.aliasing_ppgtt)) {
> > -				ret = -EEXIST;
> > -				goto err_unpin;
> > -			}
> > -
> > -			dev_priv->mm.aliasing_ppgtt = ppgtt;
> > -		}
> 
> I expect some problems with full ppgtt & this (in some places, the
> driver is still making some decisions based on
> dev_priv->mm.aliasing_ppgtt, which now will be null).  Should I address
> these problems in a subsequent patch?

Oh, good catch. I've done a bit a review and found two cases:
- Driver unload code. Already fairly broken, made much worse by my series
  here. I've fixed that up yesterday and will resend the series with those
  additional patches and revised patches.
- cmd parser. I guess that should be a fixup patch on top. I'll also do
  that.

Have you spotted any other places?

Thanks, Daniel

> 
> >  	} else if (USES_PPGTT(dev)) {
> >  		/* For platforms which only have aliasing PPGTT, we fake the
> >  		 * address space and refcounting. */
> > @@ -361,7 +350,7 @@ int i915_gem_context_init(struct drm_device *dev)
> >  		}
> >  	}
> > 
> > -	ctx = i915_gem_create_context(dev, NULL, USES_PPGTT(dev));
> > +	ctx = i915_gem_create_context(dev, NULL,
> > USES_FULL_PPGTT(dev));
> >  	if (IS_ERR(ctx)) {
> >  		DRM_ERROR("Failed to create default global context (error
> > %ld)\n",
> >  			  PTR_ERR(ctx));
> >  }
> > 
> > --
> > 1.9.3
> 



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