[Intel-gfx] [PATCH 02/20] drm/i915: Force PD restore on dirty ppGTTs

[Barbalho, Rafael]

> -----Original Message-----
> From: Ville Syrjälä [mailto:ville.syrjala at linux.intel.com]
> Sent: Thursday, May 21, 2015 4:08 PM
> To: Mika Kuoppala
> Cc: intel-gfx at lists.freedesktop.org; miku at iki.fi; Barbalho, Rafael
> Subject: Re: [Intel-gfx] [PATCH 02/20] drm/i915: Force PD restore on dirty
> ppGTTs
> 
> On Thu, May 21, 2015 at 05:37:30PM +0300, Mika Kuoppala wrote:
> > Force page directory reload when ppgtt va->pa
> > mapping has changed. Extend dirty rings mechanism
> > for gen > 7 and use it to force pd restore in execlist
> > mode when vm has been changed.
> >
> > Some parts of execlist context update cleanup based on
> > work by Chris Wilson.
> >
> > v2: Add comment about lite restore (Chris)
> >
> > Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_lrc.c | 65 ++++++++++++++++++++-------------
> -------
> >  1 file changed, 33 insertions(+), 32 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_lrc.c
> b/drivers/gpu/drm/i915/intel_lrc.c
> > index 0413b8f..5ee2a8c 100644
> > --- a/drivers/gpu/drm/i915/intel_lrc.c
> > +++ b/drivers/gpu/drm/i915/intel_lrc.c
> > @@ -264,9 +264,10 @@ u32 intel_execlists_ctx_id(struct
> drm_i915_gem_object *ctx_obj)
> >  }
> >
> >  static uint64_t execlists_ctx_descriptor(struct intel_engine_cs *ring,
> > -					 struct drm_i915_gem_object
> *ctx_obj)
> > +					 struct intel_context *ctx)
> >  {
> >  	struct drm_device *dev = ring->dev;
> > +	struct drm_i915_gem_object *ctx_obj = ctx->engine[ring->id].state;
> >  	uint64_t desc;
> >  	uint64_t lrca = i915_gem_obj_ggtt_offset(ctx_obj);
> >
> > @@ -284,6 +285,14 @@ static uint64_t execlists_ctx_descriptor(struct
> intel_engine_cs *ring,
> >  	 * signalling between Command Streamers */
> >  	/* desc |= GEN8_CTX_FORCE_RESTORE; */
> >
> > +	/* When performing a LiteRestore but with updated PD we need
> > +	 * to force the GPU to reload the PD
> > +	 */
> > +	if (intel_ring_flag(ring) & ctx->ppgtt->pd_dirty_rings) {
> > +		desc |= GEN8_CTX_FORCE_PD_RESTORE;
> 
> Wasn't there a hardware issue which basically meant you are not
> allowed to actually set this bit?
> 
> Rafael had some details on that as far as I recall so adding cc...

Ville is correct, there is a hardware issue in CHV with this bit and it should
not be set. On BDW I am not sure, although you can stop the pre-fetching
& caching in BDW by using 64-bit PPGTT addressing.

So it's no from me I'm afraid.


> 
> > +		ctx->ppgtt->pd_dirty_rings &= ~intel_ring_flag(ring);
> > +	}
> > +

<Snip>

> > --
> > 1.9.1
> >
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> > Intel-gfx at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> --
> Ville Syrjälä
> Intel OTC