How to enable AVX in a UEFI application?

poby · **Joined:** Wed Sep 21, 2016 9:39 am **Posts:** 24

I have a simple working UEFI application except avx instructions don't work. Host supports AVX and I'm using the latest version of virtualbox which supports avx and the following works (doesn't hang)

Code:

movdqa xmm0, dqword[testmem]

testmem is defined elsewhere as

Code:

align 32
testmem:   rb   128

However the following causes the program to hang up, and not proceed.

Code:

vmovdqa ymm0, qqword[testmem]

I have tried enabling AVX with

Code:

mov     rcx, 0
xgetbv
or      rax, 0007h
xsetbv 

But it doesn't help.

What am I missing?

BrightLight · **Posted:** Sun Feb 04, 2018 10:11 pm

I enable AVX this way.

Code:

   ; enable AVX
   mov rax, cr4
   or eax, 0x40000
   mov cr4, rax

   mov rcx, 0
   xgetbv

   or eax, 6
   mov rcx, 0
   xsetbv

poby · **Joined:** Wed Sep 21, 2016 9:39 am **Posts:** 24

omarrx024 wrote:

I enable AVX this way.

Code:

   ; enable AVX
   mov rax, cr4
   or eax, 0x40000
   mov cr4, rax

   mov rcx, 0
   xgetbv

   or eax, 6
   mov rcx, 0
   xsetbv

THANK YOU SOOOO MUCH!!! I've spent hours googling and reading intel manuals etc and your code just works! Awesome man!

=D>

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How to enable AVX in a UEFI application?

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