intel/ds: report when OA metric access is blocked by kernel policy

When observation_paranoid (xe) or perf_stream_paranoid (i915) prevents
unprivileged access to OA metrics, the existing code silently returns no
OA queries. PPS then fails with just a segfault.

This patch adds INTEL_PERF_FEATURE_OA_BLOCKED_BY_POLICY to
intel_perf_features, set by both KMD backends when the paranoid sysctl
exists but lacks sufficent privilage. PPS checks this flag immediately
after initialising intel_perf and returns an error before  attempting
metric-set selection.

Signed-off-by: Michael Cheng <michael.cheng@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/40898>

src/intel/ds/intel_pps_driver.cc

@@ -78,6 +78,15 @@ bool IntelDriver::init_perfcnt()
 
    perf = std::make_unique<IntelPerf>(drm_device.fd);
 
+   if (perf->cfg->features_supported & INTEL_PERF_FEATURE_OA_BLOCKED_BY_POLICY) {
+      PPS_LOG_ERROR("OA metrics access blocked by system policy "
+                    "(gpu=%d, driver=%s). "
+                    "Check kernel paranoid settings or run as root.",
+                    drm_device.gpu_num,
+                    drm_device.name.c_str());
+      return false;
+   }
+
    const char *metric_set_name = os_get_option("INTEL_PERFETTO_METRIC_SET");
 
    struct intel_perf_query_info *default_query = nullptr;

src/intel/perf/i915/intel_perf.c

@@ -148,6 +148,8 @@ i915_oa_metrics_available(struct intel_perf_config *perf, int fd, bool use_regis
 
          if (paranoid == 0 || geteuid() == 0)
             i915_perf_oa_available = true;
+         else
+            perf->features_supported |= INTEL_PERF_FEATURE_OA_BLOCKED_BY_POLICY;
       }
    }
 

src/intel/perf/intel_perf.h

@@ -430,6 +430,11 @@ enum intel_perf_features {
    INTEL_PERF_FEATURE_HOLD_PREEMPTION = (1 << 0),
    INTEL_PERF_FEATURE_GLOBAL_SSEU = (1 << 1),
    INTEL_PERF_FEATURE_METRIC_SYNC = (1 << 2),
+   /* OA metrics are supported by the kernel but access is blocked by system
+    * policy (observation_paranoid on xe, perf_stream_paranoid on i915).
+    * Set when the sysctl exists but the process lacks the required privilege.
+    */
+   INTEL_PERF_FEATURE_OA_BLOCKED_BY_POLICY = (1 << 3),
 };
 
 struct intel_perf_config {

src/intel/perf/xe/intel_perf.c

@@ -131,6 +131,8 @@ xe_oa_metrics_available(struct intel_perf_config *perf, int fd, bool use_registe
       read_file_uint64("/proc/sys/dev/xe/observation_paranoid", &paranoid);
       if (paranoid == 0 || geteuid() == 0)
          perf_oa_available = true;
+      else
+         perf->features_supported |= INTEL_PERF_FEATURE_OA_BLOCKED_BY_POLICY;
    }
 
    if (!perf_oa_available)