[Intel-gfx] [PATCH] drm/i915: Report context GTT size

[Chris Wilson]

On Wed, Oct 14, 2015 at 02:17:11PM +0100, Chris Wilson wrote:
> Since the beginning we have conflated the size of the global GTT with
> that of the per-process context sizes. In recent times (gen8+), those
> are no longer the same where the global GTT is limited to 2/4GiB but the
> per-process GTT may be anything up to 256TiB. Userspace knows nothing of
> this discrepancy and outside of one or two hacks, uses the getaperture
> ioctl to determine the maximum size it can use. Let's leave that as
> reporting the global GTT and use the context reporting method to
> describe the per-process value (which naturally fallsback to reporting
> the aliasing or global on older platforms, so userspace can always use
> this method where available).
> 
> Testcase: igt/gem_userptr_blits/minor-normal-sync
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90065
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_gem_context.c | 8 ++++++++
>  include/uapi/drm/i915_drm.h             | 5 +++--
>  2 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> index 339a9d628f1e..cecb156c6f76 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> @@ -1087,6 +1087,14 @@ int i915_gem_context_getparam_ioctl(struct drm_device *dev, void *data,
>  	case I915_CONTEXT_PARAM_NO_ZEROMAP:
>  		args->value = ctx->flags & CONTEXT_NO_ZEROMAP;
>  		break;
> +	case I915_CONTEXT_PARAM_GTT_SIZE:
> +		if (ctx->ppgtt)
> +			args->value = ctx->ppgtt->base.total;
> +		else if (to_i915(dev)->mm.aliasing_ppgtt)
> +			args->value = to_i915(dev)->mm.aliasing_ppgtt->base.total;
> +		else
> +			args->value = to_i915(dev)->gtt.base.total;
> +		break;
>  	default:
>  		ret = -EINVAL;
>  		break;
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index 83f60f01dca2..3f334967aa1b 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -1130,8 +1130,9 @@ struct drm_i915_gem_context_param {
>  	__u32 ctx_id;
>  	__u32 size;
>  	__u64 param;
> -#define I915_CONTEXT_PARAM_BAN_PERIOD 0x1
> -#define I915_CONTEXT_PARAM_NO_ZEROMAP 0x2
> +#define I915_CONTEXT_PARAM_BAN_PERIOD	0x1
> +#define I915_CONTEXT_PARAM_NO_ZEROMAP	0x2
> +#define I915_CONTEXT_PARAM_GTT_SIZE	0x3
>  	__u64 value;
>  };

Ping any takers? As ABI goes it is pretty simple...
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre