05-10-2014
Welcome to the forum.
Your post is devoid of specifics, so don't expect much targeted advice.
Are you using the CPUID instruction to detect AVX? That should work. For the specifics, there are posts on intel's site (and probably other places) demonstrating what to write/read from which registers.
However, if you actually want to use AVX, simply detecting CPU support is insufficient. Even if the CPU implements AVX, it cannot be used without operating system support (e.g. to save/restore the registers across context switches).
Regards,
Alister
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CPUID(4) Linux Programmer's Manual CPUID(4)
NAME
cpuid - x86 CPUID access device
DESCRIPTION
CPUID provides an interface for querying information about the x86 CPU.
This device is accessed by lseek (2) or pread (2) to the appropriate CPUID level and reading in chunks of 16 bytes. A larger read size
means multiple reads of consecutive levels.
The lower 32 bits of the file position is used as the incoming %eax, and the upper 32 bits of the file position as the incoming %ecx, the
latter intended for "counting" eax levels like eax=4.
This driver uses /dev/cpu/CPUNUM/cpuid, where CPUNUM is the minor number, and on an SMP box will direct the access to CPU CPUNUM as listed
in /proc/cpuinfo.
This file is protected so that it can only be read by the user root, or members of the group root.
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.
Most of the information in cpuid is reported by the kernel in cooked form either in /proc/cpuinfo or through subdirectories in
/sys/devices/system/cpu. Direct CPUID access through this device should only be used in exceptional cases.
The cpuid driver is not auto-loaded. On modular kernels you might need to use the following command to load it explicitly before use:
$ modprobe cpuid
There is no support for CPUID functions that require additional input registers.
Very old x86 CPUs don't support CPUID.
SEE ALSO
Intel Corporation, Intel 64 and IA-32 Architectures Software Developer's Manual Volume 2A: Instruction Set Reference, A-M, 3-180 CPUID ref-
erence.
Intel Corporation, Intel Processor Identification and the CPUID Instruction, Application note 485.
COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2009-03-31 CPUID(4)