Re: [PATCH 14/18] drm/i915/context: switch contexts with execbuf2

[Daniel Vetter <daniel@ffwll.ch>]

On Sun, Mar 18, 2012 at 01:39:54PM -0700, Ben Widawsky wrote:
> Use the rsvd1 field in execbuf2 to specify the context ID associated
> with the workload. This will allow the driver to do the proper context
> switch when/if needed.
> 
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
>  drivers/gpu/drm/i915/i915_gem_execbuffer.c |    6 ++++++
>  include/drm/i915_drm.h                     |    4 +++-
>  2 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> index 81687af..c365e12 100644
> --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> @@ -1058,6 +1058,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
>  	struct drm_i915_gem_object *batch_obj;
>  	struct drm_clip_rect *cliprects = NULL;
>  	struct intel_ring_buffer *ring;
> +	u32 ctx_id = args->context_info & I915_EXEC_CONTEXT_ID_MASK;
>  	u32 exec_start, exec_len;
>  	u32 seqno;
>  	u32 mask;
> @@ -1266,6 +1267,10 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
>  			goto err;
>  	}
>  
> +	ret = i915_switch_context(ring, file, ctx_id, seqno, 0);
> +	if (ret)
> +		goto err;
> +

Already complained a bit about these:
- Imo the seqno and hw_flags param can/should go away.
- You need to add some sanity checks somewhere so that we correctly bail
  out of the do_execbuffer stuff without launching the batch. Obviously
  also a prime candidate for an i-g-t tests (because it'll nicely exercise
  a piece of code which usually is rather hard to tests).

Aside: I haven't yet looked at your testcases, so maybe I'll come up with
a crazy idea for another testcase ;-)

>  	trace_i915_gem_ring_dispatch(ring, seqno);
>  
>  	exec_start = batch_obj->gtt_offset + args->batch_start_offset;
> @@ -1372,6 +1377,7 @@ i915_gem_execbuffer(struct drm_device *dev, void *data,
>  	exec2.num_cliprects = args->num_cliprects;
>  	exec2.cliprects_ptr = args->cliprects_ptr;
>  	exec2.flags = I915_EXEC_RENDER;
> +	exec2.context_info = 0;
>  
>  	ret = i915_gem_do_execbuffer(dev, data, file, &exec2, exec2_list);
>  	if (!ret) {
> diff --git a/include/drm/i915_drm.h b/include/drm/i915_drm.h
> index bead13e..03d159f 100644
> --- a/include/drm/i915_drm.h
> +++ b/include/drm/i915_drm.h
> @@ -660,13 +660,15 @@ struct drm_i915_gem_execbuffer2 {
>  #define I915_EXEC_CONSTANTS_ABSOLUTE 	(1<<6)
>  #define I915_EXEC_CONSTANTS_REL_SURFACE (2<<6) /* gen4/5 only */
>  	__u64 flags;
> -	__u64 rsvd1;
> +	__u64 context_info;
>  	__u64 rsvd2;
>  };
>  
>  /** Resets the SO write offset registers for transform feedback on gen7. */
>  #define I915_EXEC_GEN7_SOL_RESET	(1<<8)
>  
> +#define I915_EXEC_CONTEXT_ID_MASK	(0xffffffff)
> +
>  struct drm_i915_gem_pin {
>  	/** Handle of the buffer to be pinned. */
>  	__u32 handle;
> -- 
> 1.7.9.4
> 
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-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48