x86/MSR: make msr_class a static const structure

Now that the driver core allows for struct class to be in read-only
memory, move the msr_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: "H. Peter Anvin" <hpa@zytor.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
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Link: https://lore.kernel.org/r/20230620144431.583290-5-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index 7bb17d3..e17c16c 100644 (file)
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -39,7 +39,6 @@
 #include <asm/cpufeature.h>
 #include <asm/msr.h>
 
-static struct class *msr_class;
 static enum cpuhp_state cpuhp_msr_state;
 
 enum allow_write_msrs {
@@ -235,26 +234,31 @@ static const struct file_operations msr_fops = {
        .compat_ioctl = msr_ioctl,
 };
 
+static char *msr_devnode(const struct device *dev, umode_t *mode)
+{
+       return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
+}
+
+static const struct class msr_class = {
+       .name           = "msr",
+       .devnode        = msr_devnode,
+};
+
 static int msr_device_create(unsigned int cpu)
 {
        struct device *dev;
 
-       dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,
+       dev = device_create(&msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,
                            "msr%d", cpu);
        return PTR_ERR_OR_ZERO(dev);
 }
 
 static int msr_device_destroy(unsigned int cpu)
 {
-       device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
+       device_destroy(&msr_class, MKDEV(MSR_MAJOR, cpu));
        return 0;
 }
 
-static char *msr_devnode(const struct device *dev, umode_t *mode)
-{
-       return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
-}
-
 static int __init msr_init(void)
 {
        int err;
@@ -263,12 +267,9 @@ static int __init msr_init(void)
                pr_err("unable to get major %d for msr\n", MSR_MAJOR);
                return -EBUSY;
        }
-       msr_class = class_create("msr");
-       if (IS_ERR(msr_class)) {
-               err = PTR_ERR(msr_class);
+       err = class_register(&msr_class);
+       if (err)
                goto out_chrdev;
-       }
-       msr_class->devnode = msr_devnode;
 
        err  = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/msr:online",
                                 msr_device_create, msr_device_destroy);
@@ -278,7 +279,7 @@ static int __init msr_init(void)
        return 0;
 
 out_class:
-       class_destroy(msr_class);
+       class_unregister(&msr_class);
 out_chrdev:
        __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
        return err;
@@ -288,7 +289,7 @@ module_init(msr_init);
 static void __exit msr_exit(void)
 {
        cpuhp_remove_state(cpuhp_msr_state);
-       class_destroy(msr_class);
+       class_unregister(&msr_class);
        __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
 }
 module_exit(msr_exit)