[Intel-gfx] [PATCH] RFC drm/i915: Allow userspace to specify ringsize on construction

[Janusz Krzysztofik]

Hi Chris,

On Thursday, October 10, 2019 4:23:16 PM CEST Chris Wilson wrote:
> No good reason why we must always use a static ringsize, so let
> userspace select one during construction.

I've heard from UMD people they like this solution :-)

> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_context.c | 83 +++++++++++++++++++--
>  include/uapi/drm/i915_drm.h                 | 12 +++
>  2 files changed, 89 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index 46e5b3b53288..9635e377c8ae 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -455,23 +455,30 @@ __create_context(struct drm_i915_private *i915)
>  	return ERR_PTR(err);
>  }
>  
> -static void
> +static int
>  context_apply_all(struct i915_gem_context *ctx,
> -		  void (*fn)(struct intel_context *ce, void *data),
> +		  int (*fn)(struct intel_context *ce, void *data),
>  		  void *data)
>  {
>  	struct i915_gem_engines_iter it;
>  	struct intel_context *ce;
> +	int err = 0;
>  
> -	for_each_gem_engine(ce, i915_gem_context_lock_engines(ctx), it)
> -		fn(ce, data);
> +	for_each_gem_engine(ce, i915_gem_context_lock_engines(ctx), it) {
> +		err = fn(ce, data);
> +		if (err)
> +			break;
> +	}
>  	i915_gem_context_unlock_engines(ctx);
> +
> +	return err;
>  }
>  
> -static void __apply_ppgtt(struct intel_context *ce, void *vm)
> +static int __apply_ppgtt(struct intel_context *ce, void *vm)
>  {
>  	i915_vm_put(ce->vm);
>  	ce->vm = i915_vm_get(vm);
> +	return 0;
>  }
>  
>  static struct i915_address_space *
> @@ -509,9 +516,10 @@ static void __set_timeline(struct intel_timeline **dst,
>  		intel_timeline_put(old);
>  }
>  
> -static void __apply_timeline(struct intel_context *ce, void *timeline)
> +static int __apply_timeline(struct intel_context *ce, void *timeline)
>  {
>  	__set_timeline(&ce->timeline, timeline);
> +	return 0;
>  }
>  
>  static void __assign_timeline(struct i915_gem_context *ctx,
> @@ -1086,6 +1094,65 @@ static int set_ppgtt(struct drm_i915_file_private *file_priv,
>  	return err;
>  }
>  
> +static int __apply_ringsize(struct intel_context *ce, void *sz)
> +{
> +	int err = 0;
> +
> +	if (intel_context_lock_pinned(ce))
> +		return -EINTR;
> +
> +	if (intel_context_is_pinned(ce)) {
> +		err = -EBUSY; /* In active use! Come back later! */
> +		goto unlock;
> +	}
> +
> +	if (test_bit(CONTEXT_ALLOC_BIT, &ce->flags)) {
> +		struct intel_ring *ring;
> +
> +		/* Replace the existing ringbuffer */
> +		ring = intel_engine_create_ring(ce->engine,
> +						(unsigned long)sz);
> +		if (IS_ERR(ring)) {
> +			err = PTR_ERR(ring);
> +			goto unlock;
> +		}
> +
> +		intel_ring_put(ce->ring);
> +		ce->ring = ring;
> +
> +		/* Context image will be updated on next pin */
> +	} else {
> +		ce->ring = sz;
> +	}
> +
> +unlock:
> +	intel_context_unlock_pinned(ce);
> +	return err;
> +}
> +
> +static int set_ringsize(struct i915_gem_context *ctx,
> +			struct drm_i915_gem_context_param *args)
> +{
> +	if (!HAS_LOGICAL_RING_CONTEXTS(ctx->i915))
> +		return -ENODEV;
> +
> +	if (args->size)
> +		return -EINVAL;
> +
> +	if (!IS_ALIGNED(args->value, I915_GTT_PAGE_SIZE))
> +		return -EINVAL;
> +
> +	if (args->value < I915_GTT_PAGE_SIZE)
> +		return -EINVAL;
> +
> +	if (args->value > 128 * I915_GTT_PAGE_SIZE)
> +		return -EINVAL;
> +
> +	return context_apply_all(ctx,
> +				 __apply_ringsize,
> +				 __intel_context_ring_size(args->value));
> +}
> +
>  static int gen8_emit_rpcs_config(struct i915_request *rq,
>  				 struct intel_context *ce,
>  				 struct intel_sseu sseu)
> @@ -1798,6 +1865,10 @@ static int ctx_setparam(struct drm_i915_file_private *fpriv,
>  		ret = set_persistence(ctx, args);
>  		break;
>  
> +	case I915_CONTEXT_PARAM_RINGSIZE:
> +		ret = set_ringsize(ctx, args);
> +		break;
> +
>  	case I915_CONTEXT_PARAM_BAN_PERIOD:
>  	default:
>  		ret = -EINVAL;
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index eb9e704d717a..e375cd2cf66b 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -1580,6 +1580,18 @@ struct drm_i915_gem_context_param {
>   * By default, new contexts allow persistence.
>   */
>  #define I915_CONTEXT_PARAM_PERSISTENCE	0xb
> +
> +/*
> + *
> + * I915_CONTEXT_PARAM_RINGSIZE:
> + *
> + * Sets the size of the ringbuffer to use for logical ring contexts.
> + * Only possible to be set prior to first use, i.e. during construction.
> + * Only applies to the current set of engine and lost for those engines
> + * are replaced by a new mapping.
> + * Must be between 4 - 512 KiB.

nit: In case the requirement for the requested ring size to be a multiple of 4k may 
be not obvious for users, and since we don't emit a debug message if not 
satisfied, maybe we should also mention that here.  Anyway, lgtm.
Reviewed-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>

Thanks,
Janusz

> + */
> +#define I915_CONTEXT_PARAM_RINGSIZE	0xc
>  /* Must be kept compact -- no holes and well documented */
>  
>  	__u64 value;
>