Re: [PATCH v10 6/6] drm/i915: expose rcs topology through query uAPI

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 19/01/2018 13:22, Lionel Landwerlin wrote:
> With the introduction of asymmetric slices in CNL, we cannot rely on
> the previous SUBSLICE_MASK getparam to tell userspace what subslices
> are available. Here we introduce a more detailed way of querying the
> Gen's GPU topology that doesn't aggregate numbers.
> 
> This is essential for monitoring parts of the GPU with the OA unit,
> because counters need to be normalized to the number of
> EUs/subslices/slices. The current aggregated numbers like EU_TOTAL do
> not gives us sufficient information.
> 
> As a bonus we can draw representations of the GPU :
> 
>          https://imgur.com/a/vuqpa
> 
> v2: Rename uapi struct s/_mask/_info/ (Tvrtko)
>      Report max_slice/subslice/eus_per_subslice rather than strides (Tvrtko)
>      Add uapi macros to read data from *_info structs (Tvrtko)
> 
> v3: Use !!(v & DRM_I915_BIT()) for uapi macros instead of custom shifts (Tvrtko)
> 
> v4: factorize query item writting (Tvrtko)
>      tweak uapi struct/define names (Tvrtko)
> 
> v5: Replace ALIGN() macro (Chris)
> 
> v6: Updated uapi comments (Tvrtko)
>      Moved flags != 0 checks into vfuncs (Tvrtko)
> 
> v7: Use access_ok() before copying anything, to avoid overflows (Chris)
>      Switch BUG_ON() to GEM_WARN_ON() (Tvrtko)
> 
> v8: Tweak uapi comments style to match the coding style (Lionel)
> 
> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> ---
>   drivers/gpu/drm/i915/i915_query.c | 110 ++++++++++++++++++++++++++++++++++++++
>   include/uapi/drm/i915_drm.h       |  71 ++++++++++++++++++++++++
>   2 files changed, 181 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_query.c b/drivers/gpu/drm/i915/i915_query.c
> index 5aa886313cf9..ff87ec8a321a 100644
> --- a/drivers/gpu/drm/i915/i915_query.c
> +++ b/drivers/gpu/drm/i915/i915_query.c
> @@ -25,8 +25,118 @@
>   #include "i915_drv.h"
>   #include <uapi/drm/i915_drm.h>
> 
> +static int copy_query_data(struct drm_i915_query_item *query_item,
> +			   const void *item_ptr, u32 item_length,
> +			   const void *data_ptr, u32 data_length)
> +{
> +	u32 total_length = item_length + data_length;
> +
> +	if (GEM_WARN_ON(add_overflows(item_length, data_length)))
> +		return -EINVAL;
> +
> +	if (query_item->length == 0)
> +		return total_length;
> +
> +	if (query_item->length < total_length)
> +		return -EINVAL;
> +
> +	if (!access_ok(VERIFY_WRITE, u64_to_user_ptr(query_item->data_ptr),
> +		       total_length))
> +		return -EFAULT;
> +
> +	if (__copy_to_user(u64_to_user_ptr(query_item->data_ptr),
> +			   item_ptr, item_length))
> +		return -EFAULT;
> +
> +	if (__copy_to_user(u64_to_user_ptr(query_item->data_ptr + item_length),
> +			   data_ptr, data_length))
> +		return -EFAULT;
> +
> +	return total_length;
> +}
> +
> +static int query_slice_info(struct drm_i915_private *dev_priv,
> +			    struct drm_i915_query_item *query_item)
> +{
> +	const struct sseu_dev_info *sseu = &INTEL_INFO(dev_priv)->sseu;
> +	struct drm_i915_query_slice_info slice_info;
> +
> +	if (query_item->flags != 0)
> +		return -EINVAL;
> +
> +	if (sseu->max_slices == 0)
> +		return -ENODEV;
> +
> +	/*
> +	 * If we ever change the internal slice mask data type, we'll need to
> +	 * update this function.
> +	 */
> +	BUILD_BUG_ON(sizeof(u8) != sizeof(sseu->slice_mask));
> +
> +	memset(&slice_info, 0, sizeof(slice_info));
> +	slice_info.max_slices = sseu->max_slices;
> +
> +	return copy_query_data(query_item, &slice_info, sizeof(slice_info),
> +			       &sseu->slice_mask, sizeof(sseu->slice_mask));
> +}
> +
> +static int query_subslice_info(struct drm_i915_private *dev_priv,
> +			       struct drm_i915_query_item *query_item)
> +{
> +	const struct sseu_dev_info *sseu = &INTEL_INFO(dev_priv)->sseu;
> +	struct drm_i915_query_subslice_info subslice_info;
> +	u32 data_length;
> +
> +	if (query_item->flags != 0)
> +		return -EINVAL;
> +
> +	if (sseu->max_slices == 0)
> +		return -ENODEV;
> +
> +	memset(&subslice_info, 0, sizeof(subslice_info));
> +	subslice_info.max_slices = sseu->max_slices;
> +	subslice_info.max_subslices = sseu->max_subslices;
> +
> +	data_length = subslice_info.max_slices *
> +		DIV_ROUND_UP(subslice_info.max_subslices,
> +			     sizeof(sseu->subslice_mask[0]) * BITS_PER_BYTE);
> +
> +	return copy_query_data(query_item,
> +			       &subslice_info, sizeof(subslice_info),
> +			       sseu->subslice_mask, data_length);
> +}
> +
> +static int query_eu_info(struct drm_i915_private *dev_priv,
> +			 struct drm_i915_query_item *query_item)
> +{
> +	const struct sseu_dev_info *sseu = &INTEL_INFO(dev_priv)->sseu;
> +	struct drm_i915_query_eu_info eu_info;
> +	u32 data_length;
> +
> +	if (query_item->flags != 0)
> +		return -EINVAL;
> +
> +	if (sseu->max_slices == 0)
> +		return -ENODEV;
> +
> +	memset(&eu_info, 0, sizeof(eu_info));
> +	eu_info.max_slices = sseu->max_slices;
> +	eu_info.max_subslices = sseu->max_subslices;
> +	eu_info.max_eus_per_subslice = sseu->max_eus_per_subslice;
> +
> +	data_length = eu_info.max_slices * eu_info.max_subslices *
> +		DIV_ROUND_UP(eu_info.max_eus_per_subslice, BITS_PER_BYTE);
> +
> +	return copy_query_data(query_item,
> +			       &eu_info, sizeof(eu_info),
> +			       sseu->eu_mask, data_length);
> +}
> +
>   static int (* const i915_query_funcs[])(struct drm_i915_private *dev_priv,
>   					struct drm_i915_query_item *query_item) = {
> +	query_slice_info,
> +	query_subslice_info,
> +	query_eu_info,
>   };
> 
>   int i915_query_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index 03f031652d86..0a4f4cdd7e92 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -1618,6 +1618,9 @@ struct drm_i915_perf_oa_config {
> 
>   struct drm_i915_query_item {
>   	__u64 query_id;
> +#define DRM_I915_QUERY_SLICE_INFO	0x01
> +#define DRM_I915_QUERY_SUBSLICE_INFO	0x02
> +#define DRM_I915_QUERY_EU_INFO		0x03
> 
>   	/*
>   	 * When set to zero by userspace, this is filled with the size of the
> @@ -1654,6 +1657,74 @@ struct drm_i915_query {
>   	__u64 items_ptr;
>   };
> 
> +#define DRM_I915_BIT(bit) ((__u32)1 << (bit))
> +#define DRM_I915_DIV_ROUND_UP(val, div) (((val) + (div) - 1) / (div))
> +
> +/*
> + * Data written by the kernel with query DRM_I915_QUERY_SLICE_INFO :
> + *
> + * data: each bit indicates whether a slice is available (1) or fused off (0).
> + *       Formula to tell if slice X is available :
> + *
> + *            (data[X / 8] >> (X % 8)) & 1
> + *
> + *       Alternatively, use DRM_I915_QUERY_SLICE_AVAILABLE() to query a
> + *       given subslice's availability.
> + */
> +struct drm_i915_query_slice_info {
> +	__u32 max_slices;

Would it be worth also returning num_slices? I have no idea, just 
wondering if userspace cares more about the mask or count of enabled 
ones. Probably not worth it since doing the similar in other queries 
would be much harder.

> +
> +#define DRM_I915_QUERY_SLICE_AVAILABLE(info, slice) \
> +	!!((info)->data[(slice) / 8] & DRM_I915_BIT((slice) % 8))
> +	__u8 data[];
> +};
> +
> +/*
> + * Data written by the kernel with query DRM_I915_QUERY_SUBSLICE_INFO :
> + *
> + * data: each bit indicates whether a subslice is available (1) or fused off
> + *       (0). Formula to tell if slice X subslice Y is available :
> + *
> + *            (data[(X * max_subslices) + Y / 8] >> (Y % 8)) & 1

"X * max_subslices" is I think wrong, need to express the DIV_ROUND_UP 
in this comment somehow. Ah, "X * ALIGN(max_subslices, 8) / 8", as in 
the EU query?

> + *
> + *       Alternatively, use DRM_I915_QUERY_SUBSLICE_AVAILABLE() to query a
> + *       given subslice's availability.
> + */
> +struct drm_i915_query_subslice_info {
> +	__u32 max_slices;
> +	__u32 max_subslices;
> +
> +#define DRM_I915_QUERY_SUBSLICE_AVAILABLE(info, slice, subslice) \
> +	!!((info)->data[(slice) * DRM_I915_DIV_ROUND_UP((info)->max_subslices, 8) + \
> +			(subslice) / 8] & DRM_I915_BIT((subslice) % 8))
> +	__u8 data[];
> +};
> +
> +/*
> + * Data written by the kernel with query DRM_I915_QUERY_EU_INFO :
> + *
> + * data: Each bit indicates whether an EU is available (1) or fused off (0).
> + *       Formula to tell if slice X subslice Y eu Z is available :
> + *
> + *           (data[X * max_subslices * ALIGN(max_eus_per_subslice, 8) / 8 +
> + *                 Y * ALIGN(max_eus_per_subslice, 8) / 8 +
> + *                 Z / 8] >> (Z % 8)) & 1
> + *
> + *       Alternatively, use DRM_I915_QUERY_EU_AVAILABLE() to query a given
> + *       EU's availability.
> + */
> +struct drm_i915_query_eu_info {
> +	__u32 max_slices;
> +	__u32 max_subslices;
> +	__u32 max_eus_per_subslice;
> +
> +#define DRM_I915_QUERY_EU_AVAILABLE(info, slice, subslice, eu) \
> +	!!((info)->data[(slice) * DRM_I915_DIV_ROUND_UP((info)->max_eus_per_subslice, 8) * (info)->max_subslices + \
> +			(subslice) * DRM_I915_DIV_ROUND_UP((info)->max_eus_per_subslice, 8) + \
> +			(eu) / 8] & DRM_I915_BIT((eu) % 8))
> +	__u8 data[];
> +};
> +
>   #if defined(__cplusplus)
>   }
>   #endif

Regards,

Tvrtko

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