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
                         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 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
                         <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.

FILES

     /dev/cpuctl

ERRORS

     [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.

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.