drm/xe/perf/uapi: Add perf_stream_paranoid sysctl

Normally only superuser/root can access perf counter data. However,
superuser can set perf_stream_paranoid sysctl to 0 to allow non-privileged
users to also access perf data. perf_stream_paranoid is introduced at the
perf layer to allow different perf stream types to share this access
mechanism.

v2: Add kernel doc for non-static functions (Michal)
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240618014609.3233427-3-ashutosh.dixit@intel.com

drivers/gpu/drm/xe/xe_module.c

@@ -11,6 +11,7 @@
 #include "xe_drv.h"
 #include "xe_hw_fence.h"
 #include "xe_pci.h"
+#include "xe_perf.h"
 #include "xe_sched_job.h"
 
 struct xe_modparam xe_modparam = {
@@ -78,6 +79,10 @@ static const struct init_funcs init_funcs[] = {
 		.init = xe_register_pci_driver,
 		.exit = xe_unregister_pci_driver,
 	},
+	{
+		.init = xe_perf_sysctl_register,
+		.exit = xe_perf_sysctl_unregister,
+	},
 };
 
 static int __init xe_init(void)

drivers/gpu/drm/xe/xe_perf.c

@@ -4,11 +4,15 @@
  */
 
 #include <linux/errno.h>
+#include <linux/sysctl.h>
 
 #include <drm/xe_drm.h>
 
 #include "xe_perf.h"
 
+u32 xe_perf_stream_paranoid = true;
+static struct ctl_table_header *sysctl_header;
+
 /**
  * xe_perf_ioctl - The top level perf layer ioctl
  * @dev: @drm_device
@@ -32,3 +36,39 @@ int xe_perf_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
 		return -EINVAL;
 	}
 }
+
+static struct ctl_table perf_ctl_table[] = {
+	{
+	 .procname = "perf_stream_paranoid",
+	 .data = &xe_perf_stream_paranoid,
+	 .maxlen = sizeof(xe_perf_stream_paranoid),
+	 .mode = 0644,
+	 .proc_handler = proc_dointvec_minmax,
+	 .extra1 = SYSCTL_ZERO,
+	 .extra2 = SYSCTL_ONE,
+	 },
+	{}
+};
+
+/**
+ * xe_perf_sysctl_register - Register "perf_stream_paranoid" sysctl
+ *
+ * Normally only superuser/root can access perf counter data. However,
+ * superuser can set perf_stream_paranoid sysctl to 0 to allow non-privileged
+ * users to also access perf data.
+ *
+ * Return: always returns 0
+ */
+int xe_perf_sysctl_register(void)
+{
+	sysctl_header = register_sysctl("dev/xe", perf_ctl_table);
+	return 0;
+}
+
+/**
+ * xe_perf_sysctl_unregister - Unregister "perf_stream_paranoid" sysctl
+ */
+void xe_perf_sysctl_unregister(void)
+{
+	unregister_sysctl_table(sysctl_header);
+}

drivers/gpu/drm/xe/xe_perf.h

@@ -6,9 +6,15 @@
 #ifndef _XE_PERF_H_
 #define _XE_PERF_H_
 
+#include <linux/types.h>
+
 struct drm_device;
 struct drm_file;
 
+extern u32 xe_perf_stream_paranoid;
+
 int xe_perf_ioctl(struct drm_device *dev, void *data, struct drm_file *file);
+int xe_perf_sysctl_register(void);
+void xe_perf_sysctl_unregister(void);
 
 #endif