On Thu, May 07, 2015 at 03:15:50PM +0100, Robert Bragg wrote:
> + /* We bypass the default perf core perf_paranoid_cpu() ||
> + * CAP_SYS_ADMIN check by using the PERF_PMU_CAP_IS_DEVICE
> + * flag and instead authenticate based on whether the current
> + * pid owns the specified context, or require CAP_SYS_ADMIN
> + * when collecting cross-context metrics.
> + */
> + dev_priv->oa_pmu.specific_ctx = NULL;
> + if (oa_attr.single_context) {
> + u32 ctx_id = oa_attr.ctx_id;
> + unsigned int drm_fd = oa_attr.drm_fd;
> + struct fd fd = fdget(drm_fd);
> +
> + if (fd.file) {
Specify a ctx and not providing the right fd should be its own error,
either EBADF or EINVAL.
> + dev_priv->oa_pmu.specific_ctx =
> + lookup_context(dev_priv, fd.file, ctx_id);
> + }
Missing fdput
> + }
> +
> + if (!dev_priv->oa_pmu.specific_ctx && !capable(CAP_SYS_ADMIN))
> + return -EACCES;
> +
> + mutex_lock(&dev_priv->dev->struct_mutex);
i915_mutex_interruptible, probably best to couple into the GPU error
handling here as well especially as init_oa_buffer() will go onto touch
GPU internals.
> + ret = init_oa_buffer(event);
> + mutex_unlock(&dev_priv->dev->struct_mutex);
> +
> + if (ret)
> + return ret;
> +
> + BUG_ON(dev_priv->oa_pmu.exclusive_event);
> + dev_priv->oa_pmu.exclusive_event = event;
> +
> + event->destroy = i915_oa_event_destroy;
> +
> + /* PRM - observability performance counters:
> + *
> + * OACONTROL, performance counter enable, note:
> + *
> + * "When this bit is set, in order to have coherent counts,
> + * RC6 power state and trunk clock gating must be disabled.
> + * This can be achieved by programming MMIO registers as
> + * 0xA094=0 and 0xA090[31]=1"
> + *
> + * In our case we are expected that taking pm + FORCEWAKE
> + * references will effectively disable RC6 and trunk clock
> + * gating.
> + */
> + intel_runtime_pm_get(dev_priv);
> + intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL);
That is a nuisance. Aside: Why isn't OA inside the powerctx? Is a subset
valid with forcewake? It does perturb the system greatly to disable rc6,
so I wonder if it could be made optional?
> +
> + return 0;
> +}
> +
> +static void update_oacontrol(struct drm_i915_private *dev_priv)
> +{
> + BUG_ON(!spin_is_locked(&dev_priv->oa_pmu.lock));
> +
> + if (dev_priv->oa_pmu.event_active) {
> + unsigned long ctx_id = 0;
> + bool pinning_ok = false;
> +
> + if (dev_priv->oa_pmu.specific_ctx) {
> + struct intel_context *ctx =
> + dev_priv->oa_pmu.specific_ctx;
> + struct drm_i915_gem_object *obj =
> + ctx->legacy_hw_ctx.rcs_state;
If only there was ctx->legacy_hw_ctx.rcs_vma...
> +
> + if (i915_gem_obj_is_pinned(obj)) {
> + ctx_id = i915_gem_obj_ggtt_offset(obj);
> + pinning_ok = true;
> + }
> + }
> +
> + if ((ctx_id == 0 || pinning_ok)) {
> + bool periodic = dev_priv->oa_pmu.periodic;
> + u32 period_exponent = dev_priv->oa_pmu.period_exponent;
> + u32 report_format = dev_priv->oa_pmu.oa_buffer.format;
> +
> + I915_WRITE(GEN7_OACONTROL,
> + (ctx_id & GEN7_OACONTROL_CTX_MASK) |
> + (period_exponent <<
> + GEN7_OACONTROL_TIMER_PERIOD_SHIFT) |
> + (periodic ?
> + GEN7_OACONTROL_TIMER_ENABLE : 0) |
> + (report_format <<
> + GEN7_OACONTROL_FORMAT_SHIFT) |
> + (ctx_id ?
> + GEN7_OACONTROL_PER_CTX_ENABLE : 0) |
> + GEN7_OACONTROL_ENABLE);
I notice you don't use any write barriers...
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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