cpuctl (4)

Leading comments

Copyright (c) 2006-2008 Stanislav Sedov <stas@FreeBSD.org>
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
  ...

(The comments found at the beginning of the groff file "man4/cpuctl.4freebsd".)

NAME

cpuctl - cpuctl pseudo device

SYNOPSIS

To compile this driver into the kernel, place the following lines in your kernel configuration file:

device cpuctl

Alternatively, to load the driver as a module at boot time, place the following in loader.conf5:

cpuctl_load="YES"

DESCRIPTION

The special device /dev/cpuctl presents interface to the system CPU. It provides functionality to retrieve CPUID information, read/write machine specific registers (MSR) and perform CPU firmware updates.

For each CPU present in the system, the special device /dev/cpuctl%d with the appropriate index will be created. For multicore CPUs such a special device will be created for each core.

Currently, only i386 and amd64 processors are supported.

IOCTL INTERFACE

All of the supported operations are invoked using the ioctl(2) system call. Currently, the following ioctls are defined:

CPUCTL_RDMSR Fa cpuctl_msr_args_t *args

CPUCTL_WRMSR Fa cpuctl_msr_args_t *args

Read/write CPU machine specific register. The Vt cpuctl_msr_args_t structure is defined in In sys/cpuctl.h as:

typedef struct {
        int             msr;    /* MSR to read */
        uint64_t        data;
} cpuctl_msr_args_t;

CPUCTL_MSRSBIT Fa cpuctl_msr_args_t *args

CPUCTL_MSRCBIT Fa cpuctl_msr_args_t *args

Set/clear MSR bits according to the mask given in the data field.

CPUCTL_CPUID Fa cpuctl_cpuid_args_t *args

Retrieve CPUID information. Arguments are supplied in the following structure:

typedef struct {
        int             level;          /* CPUID level */
        uint32_t        data[4];
} cpuctl_cpuid_args_t;

It is equivalent to the CPUCTL_CPUID_COUNT request with level_type set to 0.

CPUCTL_CPUID_COUNT Fa cpuctl_cpuid_count_args_t *args

Retrieve CPUID information. Arguments are supplied in the following structure:

typedef struct {
        int             level;          /* CPUID level */
        int             level_type;     /* CPUID level type */
        uint32_t        data[4];
} cpuctl_cpuid_count_args_t;

The level field indicates the CPUID level to retrieve, it is loaded into the %eax register before the CPUID instruction is executed, The level_type field indicates the CPUID level type to retrieve, it is loaded into the %ecx register.

The data field is used to store the received CPUID data. That is, data[0] contains the value of %eax register after the CPUID instruction is executed, data[1] is for %ebx data[2] for %ecx and data[3] for %edx

CPUCTL_UPDATE cpuctl_update_args_t *args

Update CPU firmware (microcode). The structure is defined in In sys/cpuctl.h as:

typedef struct {
        void    *data;
        size_t  size;
} cpuctl_update_args_t;

The data field should point to the firmware image of size size

For additional information refer to cpuctl.h

RETURN VALUES

Bq Er ENXIO

The operation requested is not supported by the device (e.g., unsupported architecture or the CPU is disabled).

Bq Er EINVAL

Incorrect request was supplied, or microcode image is not correct.

Bq Er ENOMEM

No physical memory was available to complete the request.

Bq Er EFAULT

The firmware image address points outside the process address space.

FILES

/dev/cpuctl

SEE ALSO

hwpmc(4), cpucontrol(8)

HISTORY

The ifconfig driver first appeared in Fx 7.2 .

AUTHORS

The ifconfig module and this manual page were written by An Stanislav Sedov Aq stas@FreeBSD.org .

BUGS

Yes, probably, report if any.