Quoting Tvrtko Ursulin (2019-01-31 10:47:51)
> From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
>
> We want to allow userspace to reconfigure the subslice configuration on a
> per context basis.
>
> This is required for the functional requirement of shutting down non-VME
> enabled sub-slices on Gen11 parts.
>
> To do so, we expose a context parameter to allow adjustment of the RPCS
> register stored within the context image (and currently not accessible via
> LRI).
>
> If the context is adjusted before first use or whilst idle, the adjustment
> is for "free"; otherwise if the context is active we queue a request to do
> so (using the kernel context), following all other activity by that
> context, which is also marked as barrier for all following submission
> against the same context.
>
> Since the overhead of device re-configuration during context switching can
> be significant, especially in multi-context workloads, we limit this new
> uAPI to only support the Gen11 VME use case. In this use case either the
> device is fully enabled, and exactly one slice and half of the subslices
> are enabled.
>
> Example usage:
>
> struct drm_i915_gem_context_param_sseu sseu = { };
> struct drm_i915_gem_context_param arg = {
> .param = I915_CONTEXT_PARAM_SSEU,
> .ctx_id = gem_context_create(fd),
> .size = sizeof(sseu),
> .value = to_user_pointer(&sseu)
> };
>
> /* Query device defaults. */
> gem_context_get_param(fd, &arg);
>
> /* Set VME configuration on a 1x6x8 part. */
> sseu.slice_mask = 0x1;
> sseu.subslice_mask = 0xe0;
> gem_context_set_param(fd, &arg);
>
> v2: Fix offset of CTX_R_PWR_CLK_STATE in intel_lr_context_set_sseu()
> (Lionel)
>
> v3: Add ability to program this per engine (Chris)
>
> v4: Move most get_sseu() into i915_gem_context.c (Lionel)
>
> v5: Validate sseu configuration against the device's capabilities (Lionel)
>
> v6: Change context powergating settings through MI_SDM on kernel context
> (Chris)
>
> v7: Synchronize the requests following a powergating setting change using
> a global dependency (Chris)
> Iterate timelines through dev_priv.gt.active_rings (Tvrtko)
> Disable RPCS configuration setting for non capable users
> (Lionel/Tvrtko)
>
> v8: s/union intel_sseu/struct intel_sseu/ (Lionel)
> s/dev_priv/i915/ (Tvrtko)
> Change uapi class/instance fields to u16 (Tvrtko)
> Bump mask fields to 64bits (Lionel)
> Don't return EPERM when dynamic sseu is disabled (Tvrtko)
>
> v9: Import context image into kernel context's ppgtt only when
> reconfiguring powergated slice/subslices (Chris)
> Use aliasing ppgtt when needed (Michel)
>
> Tvrtko Ursulin:
>
> v10:
> * Update for upstream changes.
> * Request submit needs a RPM reference.
> * Reject on !FULL_PPGTT for simplicity.
> * Pull out get/set param to helpers for readability and less indent.
> * Use i915_request_await_dma_fence in add_global_barrier to skip waits
> on the same timeline and avoid GEM_BUG_ON.
> * No need to explicitly assign a NULL pointer to engine in legacy mode.
> * No need to move gen8_make_rpcs up.
> * Factored out global barrier as prep patch.
> * Allow to only CAP_SYS_ADMIN if !Gen11.
>
> v11:
> * Remove engine vfunc in favour of local helper. (Chris Wilson)
> * Stop retiring requests before updates since it is not needed
> (Chris Wilson)
> * Implement direct CPU update path for idle contexts. (Chris Wilson)
> * Left side dependency needs only be on the same context timeline.
> (Chris Wilson)
> * It is sufficient to order the timeline. (Chris Wilson)
> * Reject !RCS configuration attempts with -ENODEV for now.
>
> v12:
> * Rebase for make_rpcs.
>
> v13:
> * Centralize SSEU normalization to make_rpcs.
> * Type width checking (uAPI <-> implementation).
> * Gen11 restrictions uAPI checks.
> * Gen11 subslice count differences handling.
> Chris Wilson:
> * args->size handling fixes.
> * Update context image from GGTT.
> * Postpone context image update to pinning.
> * Use i915_gem_active_raw instead of last_request_on_engine.
>
> v14:
> * Add activity tracker on intel_context to fix the lifetime issues
> and simplify the code. (Chris Wilson)
>
> v15:
> * Fix context pin leak if no space in ring by simplifying the
> context pinning sequence.
>
> v16:
> * Rebase for context get/set param locking changes.
> * Just -ENODEV on !Gen11. (Joonas)
>
> v17:
> * Fix one Gen11 subslice enablement rule.
> * Handle error from i915_sw_fence_await_sw_fence_gfp. (Chris Wilson)
>
> v18:
> * Update commit message. (Joonas)
> * Restrict uAPI to VME use case. (Joonas)
>
> v19:
> * Rebase.
>
> v20:
> * Rebase for ce->active_tracker.
>
> v21:
> * Rebase for IS_GEN changes.
>
> v22:
> * Reserve uAPI for flags straight away. (Chris Wilson)
>
> v23:
> * Rebase for RUNTIME_INFO.
>
> v24:
> * Added some headline docs for the uapi usage. (Joonas/Chris)
>
> v25:
> * Renamed class/instance to engine_class/engine_instance to avoid clash
> with C++ keyword. (Tony Ye)
>
> v26:
> * Rebased for runtime pm api changes.
>
> v27:
> * Rebased for intel_context_init.
> * Wrap commit msg to 75.
>
> v28:
> (Chris Wilson)
> * Use i915_gem_ggtt.
> * Use i915_request_await_dma_fence to show a better example.
>
> v29:
> * i915_timeline_set_barrier can now fail. (Chris Wilson)
>
> v30:
> * Capture some acks.
>
> v31:
> * Drop the WARN_ON from use controllable paths. (Chris Wilson)
> * Use overflows_type for all checks.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100899
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107634
> Issue: https://github.com/intel/media-driver/issues/267
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
> Cc: Dmitry Rogozhkin <dmitry.v.rogozhkin@xxxxxxxxx>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Cc: Zhipeng Gong <zhipeng.gong@xxxxxxxxx>
> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> Cc: Tony Ye <tony.ye@xxxxxxxxx>
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> # v21
> Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> # v27
> Acked-by: Timo Aaltonen <timo.aaltonen@xxxxxxxxxxxxx>
> Acked-by: Takashi Iwai <tiwai@xxxxxxx>
Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> +static int get_sseu(struct i915_gem_context *ctx,
> + struct drm_i915_gem_context_param *args)
> +{
> + struct drm_i915_gem_context_param_sseu user_sseu;
> + struct intel_engine_cs *engine;
> + struct intel_context *ce;
> + int ret;
> +
> + if (args->size == 0)
> + goto out;
> + else if (args->size < sizeof(user_sseu))
> + return -EINVAL;
> +
> + if (copy_from_user(&user_sseu, u64_to_user_ptr(args->value),
> + sizeof(user_sseu)))
> + return -EFAULT;
> +
> + if (user_sseu.flags || user_sseu.rsvd)
> + return -EINVAL;
> +
> + engine = intel_engine_lookup_user(ctx->i915,
> + user_sseu.engine_class,
> + user_sseu.engine_instance);
> + if (!engine)
> + return -EINVAL;
> +
> + /* Only use for mutex here is to serialize get_param and set_param. */
> + ret = mutex_lock_interruptible(&ctx->i915->drm.struct_mutex);
> + if (ret)
> + return ret;
> +
> + ce = to_intel_context(ctx, engine);
Reminder to check that this keeps working with veng.
> + user_sseu.slice_mask = ce->sseu.slice_mask;
> + user_sseu.subslice_mask = ce->sseu.subslice_mask;
> + user_sseu.min_eus_per_subslice = ce->sseu.min_eus_per_subslice;
> + user_sseu.max_eus_per_subslice = ce->sseu.max_eus_per_subslice;
> +
> + mutex_unlock(&ctx->i915->drm.struct_mutex);
> +
> + if (copy_to_user(u64_to_user_ptr(args->value), &user_sseu,
> + sizeof(user_sseu)))
> + return -EFAULT;
> +
> +out:
> + args->size = sizeof(user_sseu);
> +
> + return 0;
> +}
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