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.conf(5):

             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 cpuctl_msr_args_t *args

       CPUCTL_WRMSR cpuctl_msr_args_t *args
                      Read/write CPU machine specific register.  The cpuctl_msr_args_t structure is  defined  in
                      <sys/cpuctl.h> as:

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

       CPUCTL_MSRSBIT cpuctl_msr_args_t *args

       CPUCTL_MSRCBIT cpuctl_msr_args_t *args
                      Set/clear MSR bits according to the mask given in the data field.

       CPUCTL_CPUID cpuctl_cpuid_args_t *args
                      Retrieve CPUID information.  Arguments are supplied in the following struct:

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

                      The  level  field  indicates  the  CPUID level to retrieve information for, while the data
                      field is used to store the received CPUID data.

       CPUCTL_UPDATE cpuctl_update_args_t *args
                      Update CPU firmware (microcode).  The structure is defined 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

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

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

       [ENOMEM]           No physical memory was available to complete the request.

       [EFAULT]           The firmware image address points outside the process address space.

FILES

       /dev/cpuctl

SEE ALSO

       hwpmc(4), cpucontrol(8)

HISTORY

       The cpuctl driver first appeared in FreeBSD 7.2.

AUTHORS

       The cpuctl module and this manual page were written by Stanislav Sedov <stas@FreeBSD.org>.

BUGS

       Yes, probably, report if any.

Debian                                            June 30, 2009                                        CPUCTL(4)