x86/resctrl: make pseudo_lock_class a static const structure

Now that the driver core allows for struct class to be in read-only
memory, move the pseudo_lock_class structure to be declared at build
time placing it into read-only memory, instead of having to be
dynamically allocated at boot time.

Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Reinette Chatre <reinette.chatre@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Acked-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/r/20230620144431.583290-6-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: ivanorlov2206

arch/x86/kernel/cpu/resctrl/pseudo_lock.c

@@ -45,7 +45,21 @@ static u64 prefetch_disable_bits;
  */
 static unsigned int pseudo_lock_major;
 static unsigned long pseudo_lock_minor_avail = GENMASK(MINORBITS, 0);
-static struct class *pseudo_lock_class;
+
+static char *pseudo_lock_devnode(const struct device *dev, umode_t *mode)
+{
+	const struct rdtgroup *rdtgrp;
+
+	rdtgrp = dev_get_drvdata(dev);
+	if (mode)
+		*mode = 0600;
+	return kasprintf(GFP_KERNEL, "pseudo_lock/%s", rdtgrp->kn->name);
+}
+
+static const struct class pseudo_lock_class = {
+	.name = "pseudo_lock",
+	.devnode = pseudo_lock_devnode,
+};
 
 /**
  * get_prefetch_disable_bits - prefetch disable bits of supported platforms
@@ -1353,7 +1367,7 @@ int rdtgroup_pseudo_lock_create(struct rdtgroup *rdtgrp)
 					    &pseudo_measure_fops);
 	}
 
-	dev = device_create(pseudo_lock_class, NULL,
+	dev = device_create(&pseudo_lock_class, NULL,
 			    MKDEV(pseudo_lock_major, new_minor),
 			    rdtgrp, "%s", rdtgrp->kn->name);
 
@@ -1383,7 +1397,7 @@ int rdtgroup_pseudo_lock_create(struct rdtgroup *rdtgrp)
 	goto out;
 
 out_device:
-	device_destroy(pseudo_lock_class, MKDEV(pseudo_lock_major, new_minor));
+	device_destroy(&pseudo_lock_class, MKDEV(pseudo_lock_major, new_minor));
 out_debugfs:
 	debugfs_remove_recursive(plr->debugfs_dir);
 	pseudo_lock_minor_release(new_minor);
@@ -1424,7 +1438,7 @@ void rdtgroup_pseudo_lock_remove(struct rdtgroup *rdtgrp)
 
 	pseudo_lock_cstates_relax(plr);
 	debugfs_remove_recursive(rdtgrp->plr->debugfs_dir);
-	device_destroy(pseudo_lock_class, MKDEV(pseudo_lock_major, plr->minor));
+	device_destroy(&pseudo_lock_class, MKDEV(pseudo_lock_major, plr->minor));
 	pseudo_lock_minor_release(plr->minor);
 
 free:
@@ -1560,16 +1574,6 @@ static const struct file_operations pseudo_lock_dev_fops = {
 	.mmap =		pseudo_lock_dev_mmap,
 };
 
-static char *pseudo_lock_devnode(const struct device *dev, umode_t *mode)
-{
-	const struct rdtgroup *rdtgrp;
-
-	rdtgrp = dev_get_drvdata(dev);
-	if (mode)
-		*mode = 0600;
-	return kasprintf(GFP_KERNEL, "pseudo_lock/%s", rdtgrp->kn->name);
-}
-
 int rdt_pseudo_lock_init(void)
 {
 	int ret;
@@ -1580,21 +1584,18 @@ int rdt_pseudo_lock_init(void)
 
 	pseudo_lock_major = ret;
 
-	pseudo_lock_class = class_create("pseudo_lock");
-	if (IS_ERR(pseudo_lock_class)) {
-		ret = PTR_ERR(pseudo_lock_class);
+	ret = class_register(&pseudo_lock_class);
+	if (ret) {
 		unregister_chrdev(pseudo_lock_major, "pseudo_lock");
 		return ret;
 	}
 
-	pseudo_lock_class->devnode = pseudo_lock_devnode;
 	return 0;
 }
 
 void rdt_pseudo_lock_release(void)
 {
-	class_destroy(pseudo_lock_class);
-	pseudo_lock_class = NULL;
+	class_unregister(&pseudo_lock_class);
 	unregister_chrdev(pseudo_lock_major, "pseudo_lock");
 	pseudo_lock_major = 0;
 }