[Intel-gfx] [PATCH 07/51] drm/i915: Early alloc request in execbuff

[Daniel Vetter]

On Fri, Feb 13, 2015 at 11:48:16AM +0000, John.C.Harrison at Intel.com wrote:
> From: John Harrison <John.C.Harrison at Intel.com>
> 
> Start of explicit request management in the execbuffer code path. This patch
> adds a call to allocate a request structure before all the actual hardware work
> is done. Thus guaranteeing that all that work is tagged by a known request. At
> present, nothing further is done with the request, the rest comes later in the
> series.
> 
> The only noticable change is that failure to get a request (e.g. due to lack of
> memory) will be caught earlier in the sequence. It now occurs right at the start
> before any un-undoable work has been done.
> 
> For: VIZ-5115
> Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem_execbuffer.c |   13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> index ca85803..61471e9 100644
> --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> @@ -1356,7 +1356,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
>  	const u32 ctx_id = i915_execbuffer2_get_context_id(*args);
>  	u32 dispatch_flags;
>  	int ret;
> -	bool need_relocs;
> +	bool need_relocs, batch_pinned = false;
>  
>  	if (!i915_gem_check_execbuffer(args))
>  		return -EINVAL;
> @@ -1525,10 +1525,16 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
>  		if (ret)
>  			goto err;
>  
> +		batch_pinned = true;
>  		params->batch_obj_vm_offset = i915_gem_obj_ggtt_offset(batch_obj);
>  	} else
>  		params->batch_obj_vm_offset = i915_gem_obj_offset(batch_obj, vm);
>  
> +	/* Allocate a request for this batch buffer nice and early. */
> +	ret = dev_priv->gt.alloc_request(ring, ctx);
> +	if (ret)
> +		goto err;
> +
>  	/*
>  	 * Save assorted stuff away to pass through to *_submission().
>  	 * NB: This data should be 'persistent' and not local as it will
> @@ -1544,15 +1550,16 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
>  
>  	ret = dev_priv->gt.do_execbuf(params, args, &eb->vmas);
>  
> +err:
>  	/*
>  	 * FIXME: We crucially rely upon the active tracking for the (ppgtt)
>  	 * batch vma for correctness. For less ugly and less fragility this
>  	 * needs to be adjusted to also track the ggtt batch vma properly as
>  	 * active.
>  	 */
> -	if (dispatch_flags & I915_DISPATCH_SECURE)
> +	if (batch_pinned)
>  		i915_gem_object_ggtt_unpin(batch_obj);
> -err:
> +
>  	/* the request owns the ref now */
>  	i915_gem_context_unreference(ctx);
>  	eb_destroy(eb);

This hunk here looks wrong, or maybe the context changed sufficiently
already (but I can't find that in previous patches). Why do we need to
change the pinning for the ggtt batch pin hack when allocating the request
earlier?
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch