v4.19.13 snapshot.
diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
new file mode 100644
index 0000000..ef68880
--- /dev/null
+++ b/arch/x86/kernel/msr.c
@@ -0,0 +1,244 @@
+/* ----------------------------------------------------------------------- *
+ *
+ * Copyright 2000-2008 H. Peter Anvin - All Rights Reserved
+ * Copyright 2009 Intel Corporation; author: H. Peter Anvin
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139,
+ * USA; either version 2 of the License, or (at your option) any later
+ * version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * x86 MSR access device
+ *
+ * This device is accessed by lseek() to the appropriate register number
+ * and then read/write in chunks of 8 bytes. A larger size means multiple
+ * reads or writes of the same register.
+ *
+ * This driver uses /dev/cpu/%d/msr where %d is the minor number, and on
+ * an SMP box will direct the access to CPU %d.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/fcntl.h>
+#include <linux/init.h>
+#include <linux/poll.h>
+#include <linux/smp.h>
+#include <linux/major.h>
+#include <linux/fs.h>
+#include <linux/device.h>
+#include <linux/cpu.h>
+#include <linux/notifier.h>
+#include <linux/uaccess.h>
+#include <linux/gfp.h>
+
+#include <asm/cpufeature.h>
+#include <asm/msr.h>
+
+static struct class *msr_class;
+static enum cpuhp_state cpuhp_msr_state;
+
+static ssize_t msr_read(struct file *file, char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ u32 __user *tmp = (u32 __user *) buf;
+ u32 data[2];
+ u32 reg = *ppos;
+ int cpu = iminor(file_inode(file));
+ int err = 0;
+ ssize_t bytes = 0;
+
+ if (count % 8)
+ return -EINVAL; /* Invalid chunk size */
+
+ for (; count; count -= 8) {
+ err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
+ if (err)
+ break;
+ if (copy_to_user(tmp, &data, 8)) {
+ err = -EFAULT;
+ break;
+ }
+ tmp += 2;
+ bytes += 8;
+ }
+
+ return bytes ? bytes : err;
+}
+
+static ssize_t msr_write(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ const u32 __user *tmp = (const u32 __user *)buf;
+ u32 data[2];
+ u32 reg = *ppos;
+ int cpu = iminor(file_inode(file));
+ int err = 0;
+ ssize_t bytes = 0;
+
+ if (count % 8)
+ return -EINVAL; /* Invalid chunk size */
+
+ for (; count; count -= 8) {
+ if (copy_from_user(&data, tmp, 8)) {
+ err = -EFAULT;
+ break;
+ }
+ err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);
+ if (err)
+ break;
+ tmp += 2;
+ bytes += 8;
+ }
+
+ return bytes ? bytes : err;
+}
+
+static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
+{
+ u32 __user *uregs = (u32 __user *)arg;
+ u32 regs[8];
+ int cpu = iminor(file_inode(file));
+ int err;
+
+ switch (ioc) {
+ case X86_IOC_RDMSR_REGS:
+ if (!(file->f_mode & FMODE_READ)) {
+ err = -EBADF;
+ break;
+ }
+ if (copy_from_user(®s, uregs, sizeof regs)) {
+ err = -EFAULT;
+ break;
+ }
+ err = rdmsr_safe_regs_on_cpu(cpu, regs);
+ if (err)
+ break;
+ if (copy_to_user(uregs, ®s, sizeof regs))
+ err = -EFAULT;
+ break;
+
+ case X86_IOC_WRMSR_REGS:
+ if (!(file->f_mode & FMODE_WRITE)) {
+ err = -EBADF;
+ break;
+ }
+ if (copy_from_user(®s, uregs, sizeof regs)) {
+ err = -EFAULT;
+ break;
+ }
+ err = wrmsr_safe_regs_on_cpu(cpu, regs);
+ if (err)
+ break;
+ if (copy_to_user(uregs, ®s, sizeof regs))
+ err = -EFAULT;
+ break;
+
+ default:
+ err = -ENOTTY;
+ break;
+ }
+
+ return err;
+}
+
+static int msr_open(struct inode *inode, struct file *file)
+{
+ unsigned int cpu = iminor(file_inode(file));
+ struct cpuinfo_x86 *c;
+
+ if (!capable(CAP_SYS_RAWIO))
+ return -EPERM;
+
+ if (cpu >= nr_cpu_ids || !cpu_online(cpu))
+ return -ENXIO; /* No such CPU */
+
+ c = &cpu_data(cpu);
+ if (!cpu_has(c, X86_FEATURE_MSR))
+ return -EIO; /* MSR not supported */
+
+ return 0;
+}
+
+/*
+ * File operations we support
+ */
+static const struct file_operations msr_fops = {
+ .owner = THIS_MODULE,
+ .llseek = no_seek_end_llseek,
+ .read = msr_read,
+ .write = msr_write,
+ .open = msr_open,
+ .unlocked_ioctl = msr_ioctl,
+ .compat_ioctl = msr_ioctl,
+};
+
+static int msr_device_create(unsigned int cpu)
+{
+ struct device *dev;
+
+ 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));
+ return 0;
+}
+
+static char *msr_devnode(struct device *dev, umode_t *mode)
+{
+ return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
+}
+
+static int __init msr_init(void)
+{
+ int err;
+
+ if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {
+ pr_err("unable to get major %d for msr\n", MSR_MAJOR);
+ return -EBUSY;
+ }
+ msr_class = class_create(THIS_MODULE, "msr");
+ if (IS_ERR(msr_class)) {
+ err = PTR_ERR(msr_class);
+ 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);
+ if (err < 0)
+ goto out_class;
+ cpuhp_msr_state = err;
+ return 0;
+
+out_class:
+ class_destroy(msr_class);
+out_chrdev:
+ __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
+ return err;
+}
+module_init(msr_init);
+
+static void __exit msr_exit(void)
+{
+ cpuhp_remove_state(cpuhp_msr_state);
+ class_destroy(msr_class);
+ __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
+}
+module_exit(msr_exit)
+
+MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
+MODULE_DESCRIPTION("x86 generic MSR driver");
+MODULE_LICENSE("GPL");