On Thu, 2017-11-02 at 12:42 +0000, Chris Wilson wrote:
> Take a copy of the HW state after a reset upon module loading by
> executing a context switch from a blank context to the kernel context,
> thus saving the default hw state over the blank context image.
> We can then use the default hw state to initialise any future context,
> ensuring that each starts with the default view of hw state.
> 
> Signed-off-by: Chris Wilson <[email protected]>

<SNIP>

> @@ -795,11 +770,7 @@ static int do_rcs_switch(struct drm_i915_gem_request 
> *req)
>                       return ret;
>       }
>  
> -     if (!to->engine[RCS].initialised || i915_gem_context_is_default(to))
> -             /* NB: If we inhibit the restore, the context is not allowed to
> -              * die because future work may end up depending on valid address
> -              * space. This means we must enforce that a page table load
> -              * occur when this occurs. */

Maybe add a comment explaining that we never ever assume execution on
the kernel context, so we don't care about the register state.

> +     if (i915_gem_context_is_kernel(to))
>               hw_flags = MI_RESTORE_INHIBIT;
>       else if (ppgtt && intel_engine_flag(engine) & ppgtt->pd_dirty_rings)
>               hw_flags = MI_FORCE_RESTORE;

<SNIP>

> @@ -2193,11 +2184,28 @@ populate_lr_context(struct i915_gem_context *ctx,
>       }
>       ctx_obj->mm.dirty = true;
>  
> +     if (engine->default_state) {
> +             void *defaults;
> +
> +             defaults = i915_gem_object_pin_map(engine->default_state,
> +                                                I915_MAP_WB);
> +             if (IS_ERR(defaults))
> +                     return PTR_ERR(defaults);
> +
> +             memcpy(vaddr + LRC_HEADER_PAGES * PAGE_SIZE,
> +                    defaults + LRC_HEADER_PAGES * PAGE_SIZE,

Could use somethingsomething_offset variable.

Reviewed-by: Joonas Lahtinen <[email protected]>

Regards, Joonas
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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