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AVX Support https://forum.osdev.org/viewtopic.php?f=13&t=31928 |
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Author: | tsdnz [ Thu May 18, 2017 3:25 pm ] |
Post subject: | AVX Support |
Hi, I am adding AVX support to my OS. Does AVX only work in protected mode? I get an Invalid Opcode exception I have setup AVX support and the server has AVX Under exceptions in the docs it looks like AVX is only supported in Protected Mode. Anyone else come across this? Ali |
Author: | tsdnz [ Thu May 18, 2017 3:29 pm ] |
Post subject: | Re: AVX Support |
The instruction causing the exception is vldmxcsr |
Author: | JAAman [ Fri May 19, 2017 9:03 am ] |
Post subject: | Re: AVX Support |
Intel volume 2, section LDMXCSR wrote: Note: In VEX-encoded versions, VEX.vvvv is reserved and must be 1111b, otherwise instructions will #UD. Intel LDMXCSR: Exceptions wrote: #UD If VEX.vvvv ≠ 1111B. also, Intel manual volume 2, 2.4.5 Exceptions Type 5 includes a table (labeled table 2-22 in my latest edition) gives a list of causes of various causes for exceptions in various modes in #UD in RMode for type 5 exception-class can be caused by: -VEX prefix -legacy SSE instructions if CR0.EM=1 or CR4.OSFXSR=0 -if preceded by lock instruction -if any corresponding CPUID feature flag is 0 there is nothing in the "ldmxcsr" section that says it only works in PMode |
Author: | tsdnz [ Fri May 19, 2017 5:29 pm ] |
Post subject: | Re: AVX Support |
Cheers for the reply, it reminded me to have another look. I had two issues.
Thanks for your reply. Ali |
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