Re: [PATCH 08/17] drm/i915: Don't look at pg_dirty_rings for aliasing ppgtt

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Apr 14, 2015 at 06:53:41PM +0100, Chris Wilson wrote:
> On Tue, Apr 14, 2015 at 07:11:25PM +0200, Daniel Vetter wrote:
> > On Tue, Apr 14, 2015 at 05:06:36PM +0100, Chris Wilson wrote:
> > > On Tue, Apr 14, 2015 at 05:35:18PM +0200, Daniel Vetter wrote:
> > > > We load the ppgtt ptes once per gpu reset/driver load/resume and
> > > > that's all that's needed. Note that this only blows up when we're
> > > > using the allocate_va_range funcs and not the special-purpose ones
> > > > used. With this change we can get rid of that duplication.
> > > 
> > > Honestly, I would prefer the test to be rewritten so that the
> > > information on which vm was being used was passed along and not that
> > > magic sprinkled in the middle of nowhere. e.g. execbuffer knows exactly
> > > what vm it bound the objects into, and yet towards the end we decide to
> > > guess again. Also, I would rather the execbuffer test be moved to
> > > i915_gem_context since it is scattering internal knowledge about.
> > 
> > Yeah I agree that there's more room for cleanup. I've done this minimal
> > patch purely to shut up the bogus WARN_ONs when I tried to unify the
> > gen6/7 pt alloc code in the next patch. Since it's bogus.
> 
> How about:

Yeah, but imo there's also more. I tried to understand the gen8 legacy ctx
switch logic and failed, and I wasn't fully convinced that the gen7 one
won't WARN if we actually enable full ppgtt. Given all that I decided to
go with the most minimal patch and just removed the offending bogus WARN.
But Mika/Michel promised to hang around for eventual cleanups?
-Daniel

> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> index ed9232126644..be0f475ee1e5 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> @@ -638,22 +638,14 @@ mi_set_context(struct intel_engine_cs *ring,
>  
>  static inline bool should_skip_switch(struct intel_engine_cs *ring,
>                                       struct intel_context *from,
> -                                     struct intel_context *to)
> +                                     struct intel_context *to,
> +                                     struct i915_hw_ppgtt *ppgtt)
>  {
> -       struct drm_i915_private *dev_priv = ring->dev->dev_private;
> -
>         if (to->remap_slice)
>                 return false;
>  
> -       if (to->ppgtt) {
> -               if (from == to && !test_bit(ring->id,
> -                               &to->ppgtt->pd_dirty_rings))
> -                       return true;
> -       } else if (dev_priv->mm.aliasing_ppgtt) {
> -               if (from == to && !test_bit(ring->id,
> -                               &dev_priv->mm.aliasing_ppgtt->pd_dirty_rings))
> -                       return true;
> -       }
> +       if (from == to && !test_bit(ring->id, &ppgtt->pd_dirty_rings))
> +               return true;
>  
>         return false;
>  }
> @@ -661,15 +653,13 @@ static inline bool should_skip_switch(struct intel_engine_cs *ring,
>  static bool
>  needs_pd_load_pre(struct intel_engine_cs *ring, struct intel_context *to)
>  {
> -       struct drm_i915_private *dev_priv = ring->dev->dev_private;
> -
>         if (!to->ppgtt)
>                 return false;
>  
>         if (INTEL_INFO(ring->dev)->gen < 8)
>                 return true;
>  
> -       if (ring != &dev_priv->ring[RCS])
> +       if (ring->id != RCS)
>                 return true;
>  
>         return false;
> @@ -679,15 +669,13 @@ static bool
>  needs_pd_load_post(struct intel_engine_cs *ring, struct intel_context *to,
>                 u32 hw_flags)
>  {
> -       struct drm_i915_private *dev_priv = ring->dev->dev_private;
> -
>         if (!to->ppgtt)
>                 return false;
>  
>         if (!IS_GEN8(ring->dev))
>                 return false;
>  
> -       if (ring != &dev_priv->ring[RCS])
> +       if (ring->id != RCS)
>                 return false;
>  
>         if (hw_flags & MI_RESTORE_INHIBIT)
> @@ -701,14 +689,15 @@ static int do_switch(struct intel_engine_cs *ring,
>  {
>         struct drm_i915_private *dev_priv = ring->dev->dev_private;
>         struct intel_context *from = ring->last_context;
> +       struct i915_hw_ppgtt *ppgtt = to->ppgtt ?: dev_priv->mm.aliasing_ppgtt;
>         u32 hw_flags = 0;
>         bool uninitialized = false;
>         int ret, i;
>  
> -       if (from != NULL && ring == &dev_priv->ring[RCS])
> +       if (from != NULL && ring->id == RCS)
>                 BUG_ON(from->legacy_hw_ctx.rcs_vma == NULL);
>  
> -       if (should_skip_switch(ring, from, to))
> +       if (should_skip_switch(ring, from, to, ppgtt))
>                 return 0;
>  
>         /* Trying to pin first makes error handling easier. */
> @@ -851,6 +840,9 @@ done:
>         i915_gem_context_reference(to);
>         ring->last_context = to;
>  
> +       WARN(ppgtt->pd_dirty_rings & (1<<ring->id),
> +            "%s didn't clear reload\n", ring->name);
> +
>         if (uninitialized) {
>                 if (ring->init_context) {
>                         ret = ring->init_context(ring, to);
> diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> index ef644e7eaac0..595daecb3283 100644
> --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> @@ -1385,13 +1385,6 @@ i915_gem_ringbuffer_submission(struct drm_device *dev, struct drm_file *file,
>         if (ret)
>                 goto error;
>  
> -       if (ctx->ppgtt)
> -               WARN(ctx->ppgtt->pd_dirty_rings & (1<<ring->id),
> -                       "%s didn't clear reload\n", ring->name);
> -       else if (dev_priv->mm.aliasing_ppgtt)
> -               WARN(dev_priv->mm.aliasing_ppgtt->pd_dirty_rings &
> -                       (1<<ring->id), "%s didn't clear reload\n", ring->name);
> -
>         instp_mode = args->flags & I915_EXEC_CONSTANTS_MASK;
>         instp_mask = I915_EXEC_CONSTANTS_MASK;
>         switch (instp_mode) {
> 
> 
> It gets rid of the internal knowledge of address spaces from the execbuf
> code, and keeps the symmetry between handling aliasing_ppgtt and
> full_ppgtt. (The former should just be a degenerate case where the PD
> are all preloaded).
> -Chris
> 
> -- 
> Chris Wilson, Intel Open Source Technology Centre

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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