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-.\" Copyright (c) 2009 Intel Corporation, Author Andi Kleen
-.\" Description based on comments in arch/x86/kernel/cpuid.c
-.\"
-.\" SPDX-License-Identifier: Linux-man-pages-copyleft
-.\"
-.TH cpuid 4 2024-01-05 "Linux man-pages 6.7"
-.SH NAME
-cpuid \- x86 CPUID access device
-.SH DESCRIPTION
-CPUID provides an interface for querying information about the x86 CPU.
-.P
-This device is accessed by
-.BR lseek (2)
-or
-.BR pread (2)
-to the appropriate CPUID level and reading in chunks of 16 bytes.
-A larger read size means multiple reads of consecutive levels.
-.P
-The lower 32 bits of the file position is used as the incoming
-.IR %eax ,
-and the upper 32 bits of the file position as the incoming
-.IR %ecx ,
-the latter is intended for "counting"
-.I eax
-levels like
-.IR eax=4 .
-.P
-This driver uses
-.IR /dev/cpu/CPUNUM/cpuid ,
-where
-.I CPUNUM
-is the minor number,
-and on an SMP box will direct the access to CPU
-.I CPUNUM
-as listed in
-.IR /proc/cpuinfo .
-.P
-This file is protected so that it can be read only by the user
-.IR root ,
-or members of the group
-.IR root .
-.SH NOTES
-The CPUID instruction can be directly executed by a program
-using inline assembler.
-However this device allows convenient
-access to all CPUs without changing process affinity.
-.P
-Most of the information in
-.I cpuid
-is reported by the kernel in cooked form either in
-.I /proc/cpuinfo
-or through subdirectories in
-.IR /sys/devices/system/cpu .
-Direct CPUID access through this device should only
-be used in exceptional cases.
-.P
-The
-.I cpuid
-driver is not auto-loaded.
-On modular kernels you might need to use the following command
-to load it explicitly before use:
-.P
-.in +4n
-.EX
-$ modprobe cpuid
-.EE
-.in
-.P
-There is no support for CPUID functions that require additional
-input registers.
-.P
-Early i486 CPUs do not support the CPUID instruction;
-.\" arch/x86/kernel/cpuid.c cpuid_open()
-opening this device for those CPUs fails with EIO.
-.SH SEE ALSO
-.BR cpuid (1)
-.P
-Intel Corporation, Intel 64 and IA-32 Architectures
-Software Developer's Manual Volume 2A:
-Instruction Set Reference, A-M, 3-180 CPUID reference.
-.P
-Intel Corporation, Intel Processor Identification and
-the CPUID Instruction, Application note 485.