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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.

BUGS

     Yes, probably, report if any.

AUTHORS

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