s390-vfio-ap: introduces s390 kernel debug feature for vfio_ap device driver

Sets up an s390dbf debug log for the vfio_ap device driver for logging
events occurring during the lifetime of the driver.
Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

drivers/s390/crypto/vfio_ap_debug.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ *  Copyright IBM Corp. 2022
+ *
+ * Author(s): Tony Krowiak <akrowiak@linux.ibm.com>
+ */
+#ifndef VFIO_AP_DEBUG_H
+#define VFIO_AP_DEBUG_H
+
+#include <asm/debug.h>
+
+#define DBF_ERR		3	/* error conditions   */
+#define DBF_WARN	4	/* warning conditions */
+#define DBF_INFO	5	/* informational      */
+#define DBF_DEBUG	6	/* for debugging only */
+
+#define DBF_MAX_SPRINTF_ARGS 10
+
+#define VFIO_AP_DBF(...)					\
+	debug_sprintf_event(vfio_ap_dbf_info, ##__VA_ARGS__)
+#define VFIO_AP_DBF_ERR(...)					\
+	debug_sprintf_event(vfio_ap_dbf_info, DBF_ERR, ##__VA_ARGS__)
+#define VFIO_AP_DBF_WARN(...)					\
+	debug_sprintf_event(vfio_ap_dbf_info, DBF_WARN, ##__VA_ARGS__)
+#define VFIO_AP_DBF_INFO(...)					\
+	debug_sprintf_event(vfio_ap_dbf_info, DBF_INFO, ##__VA_ARGS__)
+#define VFIO_AP_DBF_DBG(...)					\
+	debug_sprintf_event(vfio_ap_dbf_info, DBF_DEBUG, ##__VA_ARGS__)
+
+extern debug_info_t *vfio_ap_dbf_info;
+
+#endif /* VFIO_AP_DEBUG_H */

drivers/s390/crypto/vfio_ap_drv.c

@@ -14,6 +14,7 @@
 #include <linux/string.h>
 #include <asm/facility.h>
 #include "vfio_ap_private.h"
+#include "vfio_ap_debug.h"
 
 #define VFIO_AP_ROOT_NAME "vfio_ap"
 #define VFIO_AP_DEV_NAME "matrix"
@@ -26,6 +27,7 @@ MODULE_DESCRIPTION("VFIO AP device driver, Copyright IBM Corp. 2018");
 MODULE_LICENSE("GPL v2");
 
 struct ap_matrix_dev *matrix_dev;
+debug_info_t *vfio_ap_dbf_info;
 
 /* Only type 10 adapters (CEX4 and later) are supported
  * by the AP matrix device driver
@@ -250,10 +252,28 @@ static void vfio_ap_matrix_dev_destroy(void)
 	root_device_unregister(root_device);
 }
 
+static int __init vfio_ap_dbf_info_init(void)
+{
+	vfio_ap_dbf_info = debug_register("vfio_ap", 1, 1,
+					  DBF_MAX_SPRINTF_ARGS * sizeof(long));
+
+	if (!vfio_ap_dbf_info)
+		return -ENOENT;
+
+	debug_register_view(vfio_ap_dbf_info, &debug_sprintf_view);
+	debug_set_level(vfio_ap_dbf_info, DBF_WARN);
+
+	return 0;
+}
+
 static int __init vfio_ap_init(void)
 {
 	int ret;
 
+	ret = vfio_ap_dbf_info_init();
+	if (ret)
+		return ret;
+
 	/* If there are no AP instructions, there is nothing to pass through. */
 	if (!ap_instructions_available())
 		return -ENODEV;
@@ -284,6 +304,7 @@ static void __exit vfio_ap_exit(void)
 	vfio_ap_mdev_unregister();
 	ap_driver_unregister(&vfio_ap_drv);
 	vfio_ap_matrix_dev_destroy();
+	debug_unregister(vfio_ap_dbf_info);
 }
 
 module_init(vfio_ap_init);