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CPUCTL(4)              FreeBSD Kernel Interfaces Manual              CPUCTL(4)

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_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>.

FreeBSD 11.0-PRERELEASE          May 31, 2008          FreeBSD 11.0-PRERELEASE

NAME | SYNOPSIS | DESCRIPTION | IOCTL INTERFACE | RETURN VALUES | FILES | SEE ALSO | HISTORY | BUGS | AUTHORS

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