CPUCTL (4)
BSD 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_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;
BSD
June 30, 2009
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CPUCTL (4)
BSD Kernel Interfaces Manual
CPUCTL (4)
} cpuctl_update_args_t;
The data field should point to the firmware image of size size.
For additional information refer to cpuctl.h.
RET