[Intel-gfx] [PATCH v2 4/6] drm/i915/sseu: Don't try to store EU mask internally in UAPI format
Tvrtko Ursulin
tvrtko.ursulin at linux.intel.com
Fri May 20 09:32:59 UTC 2022
On 17/05/2022 04:20, Matt Roper wrote:
> Storing the EU mask internally in the same format the I915_QUERY
> topology queries use makes the final copy_to_user() a bit simpler, but
> makes the rest of the driver's SSEU more complicated and harder to
> follow. Let's switch to an internal representation that's more natural:
> Xe_HP platforms will be a simple array of u16 masks, whereas pre-Xe_HP
> platforms will be a two-dimensional array, indexed by [slice][subslice].
> We'll convert to the uapi format only when the query uapi is called.
>
> v2:
> - Drop has_common_ss_eumask. We waste some space repeating identical
> EU masks for every single DSS, but the code is simpler without it.
> (Tvrtko)
>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
> ---
> drivers/gpu/drm/i915/gt/intel_sseu.c | 77 +++++++++++++++++++---------
> drivers/gpu/drm/i915/gt/intel_sseu.h | 9 +++-
> drivers/gpu/drm/i915/i915_query.c | 8 +--
> 3 files changed, 65 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_sseu.c b/drivers/gpu/drm/i915/gt/intel_sseu.c
> index ade3e1805782..d89e2e0f05e5 100644
> --- a/drivers/gpu/drm/i915/gt/intel_sseu.c
> +++ b/drivers/gpu/drm/i915/gt/intel_sseu.c
> @@ -78,47 +78,76 @@ intel_sseu_subslices_per_slice(const struct sseu_dev_info *sseu, u8 slice)
> return hweight32(intel_sseu_get_subslices(sseu, slice));
> }
>
> -static int sseu_eu_idx(const struct sseu_dev_info *sseu, int slice,
> - int subslice)
> -{
> - int slice_stride = sseu->max_subslices * sseu->eu_stride;
> -
> - return slice * slice_stride + subslice * sseu->eu_stride;
> -}
> -
> static u16 sseu_get_eus(const struct sseu_dev_info *sseu, int slice,
> int subslice)
> {
> - int i, offset = sseu_eu_idx(sseu, slice, subslice);
> - u16 eu_mask = 0;
> -
> - for (i = 0; i < sseu->eu_stride; i++)
> - eu_mask |=
> - ((u16)sseu->eu_mask[offset + i]) << (i * BITS_PER_BYTE);
> -
> - return eu_mask;
> + if (sseu->has_xehp_dss) {
> + WARN_ON(slice > 0);
> + return sseu->eu_mask.xehp[subslice];
> + } else {
> + return sseu->eu_mask.hsw[slice][subslice];
> + }
> }
>
> static void sseu_set_eus(struct sseu_dev_info *sseu, int slice, int subslice,
> u16 eu_mask)
> {
> - int i, offset = sseu_eu_idx(sseu, slice, subslice);
> -
> - for (i = 0; i < sseu->eu_stride; i++)
> - sseu->eu_mask[offset + i] =
> - (eu_mask >> (BITS_PER_BYTE * i)) & 0xff;
> + if (sseu->has_xehp_dss) {
> + WARN_ON(slice > 0);
> + sseu->eu_mask.xehp[subslice] = eu_mask;
> + } else {
> + eu_mask &= GENMASK(sseu->max_eus_per_subslice - 1, 0);
Is this masking required? Oh I remember.. it's the type expansion! I thought that was wrong. I mean the callers are wrong. Some use u8 for the mask and then do ~mask passing it into u16 here. I don't think this function should account for that but callers should stop passing in garbage.
I had this in my patch:
GEM_WARN_ON(mask && (__fls(mask) >= sseu->max_eus_per_subslice));
And in the callers like:
- sseu_set_eus(sseu, 0, 0, ~disabled_mask);
+ sseu_set_eus(sseu, 0, 0, ~disabled_mask & 0xff);
- sseu_set_eus(sseu, s, ss, ~eu_disabled_mask);
+ sseu_set_eus(sseu, s, ss, ~eu_disabled_mask & eu_mask);
> + sseu->eu_mask.hsw[slice][subslice] = eu_mask;
> + }
> }
>
> static u16 compute_eu_total(const struct sseu_dev_info *sseu)
> {
> - u16 i, total = 0;
> + int s, ss, total = 0;
>
> - for (i = 0; i < ARRAY_SIZE(sseu->eu_mask); i++)
> - total += hweight8(sseu->eu_mask[i]);
> + for (s = 0; s < sseu->max_slices; s++)
> + for (ss = 0; ss < sseu->max_subslices; ss++)
> + if (sseu->has_xehp_dss)
> + total += hweight16(sseu->eu_mask.xehp[ss]);
> + else
> + total += hweight16(sseu->eu_mask.hsw[s][ss]);
>
> return total;
> }
>
> +/**
> + * intel_sseu_copy_eumask_to_user - Copy EU mask into a userspace buffer
> + * @to: Pointer to userspace buffer to copy to
> + * @sseu: SSEU structure containing EU mask to copy
> + *
> + * Copies the EU mask to a userspace buffer in the format expected by
> + * the query ioctl's topology queries.
> + *
> + * Returns the result of the copy_to_user() operation.
> + */
> +int intel_sseu_copy_eumask_to_user(void __user *to,
> + const struct sseu_dev_info *sseu)
> +{
> + u8 eu_mask[GEN_SS_MASK_SIZE * GEN_MAX_EU_STRIDE] = {};
> + int len = sseu->max_slices * sseu->max_subslices * sseu->eu_stride;
How compilcated to kick eu_stride out of kernel struct sseu_dev_info and just calculate it here? Since I don't think it belongs in the kernel struct.
What about ss_stride - is that still in use at this point, or by the end of the series, and could it be dropped?
Regards,
Tvrtko
> + int s, ss, i;
> +
> + for (s = 0; s < sseu->max_slices; s++) {
> + for (ss = 0; ss < sseu->max_subslices; ss++) {
> + int uapi_offset =
> + s * sseu->max_subslices * sseu->eu_stride +
> + ss * sseu->eu_stride;
> + u16 mask = sseu_get_eus(sseu, s, ss);
> +
> + for (i = 0; i < sseu->eu_stride; i++)
> + eu_mask[uapi_offset + i] =
> + (mask >> (BITS_PER_BYTE * i)) & 0xff;
> + }
> + }
> +
> + return copy_to_user(to, eu_mask, len);
> +}
> +
> static void gen11_compute_sseu_info(struct sseu_dev_info *sseu,
> u32 g_ss_en, u32 c_ss_en, u16 eu_en)
> {
> diff --git a/drivers/gpu/drm/i915/gt/intel_sseu.h b/drivers/gpu/drm/i915/gt/intel_sseu.h
> index 4a041f9dc490..43a8f8f98687 100644
> --- a/drivers/gpu/drm/i915/gt/intel_sseu.h
> +++ b/drivers/gpu/drm/i915/gt/intel_sseu.h
> @@ -57,7 +57,11 @@ struct sseu_dev_info {
> u8 subslice_mask[GEN_SS_MASK_SIZE];
> u8 geometry_subslice_mask[GEN_SS_MASK_SIZE];
> u8 compute_subslice_mask[GEN_SS_MASK_SIZE];
> - u8 eu_mask[GEN_SS_MASK_SIZE * GEN_MAX_EU_STRIDE];
> + union {
> + u16 hsw[GEN_MAX_HSW_SLICES][GEN_MAX_SS_PER_HSW_SLICE];
> + u16 xehp[GEN_MAX_DSS];
> + } eu_mask;
> +
> u16 eu_total;
> u8 eu_per_subslice;
> u8 min_eu_in_pool;
> @@ -150,4 +154,7 @@ void intel_sseu_print_topology(struct drm_i915_private *i915,
>
> u16 intel_slicemask_from_dssmask(u64 dss_mask, int dss_per_slice);
>
> +int intel_sseu_copy_eumask_to_user(void __user *to,
> + const struct sseu_dev_info *sseu);
> +
> #endif /* __INTEL_SSEU_H__ */
> diff --git a/drivers/gpu/drm/i915/i915_query.c b/drivers/gpu/drm/i915/i915_query.c
> index 7584cec53d5d..16f43bf32a05 100644
> --- a/drivers/gpu/drm/i915/i915_query.c
> +++ b/drivers/gpu/drm/i915/i915_query.c
> @@ -76,10 +76,10 @@ static int fill_topology_info(const struct sseu_dev_info *sseu,
> subslice_mask, subslice_length))
> return -EFAULT;
>
> - if (copy_to_user(u64_to_user_ptr(query_item->data_ptr +
> - sizeof(topo) +
> - slice_length + subslice_length),
> - sseu->eu_mask, eu_length))
> + if (intel_sseu_copy_eumask_to_user(u64_to_user_ptr(query_item->data_ptr +
> + sizeof(topo) +
> + slice_length + subslice_length),
> + sseu))
> return -EFAULT;
>
> return total_length;
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