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Does Anybody know why the same procedure that I use for FPU initialization works for BSP core but not for AP?

I don't know which detail I can provide.

I read Intel reference for FPU exception, by now I can't find any help to resolve so I try to ask here!

Combuster wrote:

I read Intel reference for FPU exception, by now I can't find any help to resolve so I try to ask here!

You missed the point. You get an exception, that means you have an exception number, instruction causing the fault, and a CPU state. Have you gone through all the options listed under that instruction (intel 2A/B) to see what caused the fault in question? Have you gone through all the common causes for that exception (intel 3A) and eliminated them one by one?

If no, you have some work to do .

If yes, you did something wrong. Post the state mentioned above, and the list of causes in the manual and explain to us, for each of them, why they can not be the cause. That way we can actually see the mistake and help you out.

When the x87 FPU detects stack overflow or underflow, it sets the IE flag (bit 0) and
the SF flag (bit 6) in the x87 FPU status word to 1. It then sets condition-code flag C1
(bit 9) in the x87 FPU status word to 1 if stack overflow occurred or to 0 if stack
underflow occurred.

Combuster wrote:So it is a FPU stack overflow. What does that mean? Can you make one occur under any condition? What do you need to make that happen? How can you prevent that from happening?

Debugging effort is not about spending x minutes on the task and then asking, it requires that you spent at least x minutes on every clue you get. If you discover something possibly related to the problem, it means you have even more debugging to do. Unless, of course, you found the source of the problem.

Bad questions involve "I walked 10 miles, I'm bored. Can someone drive me the last two miles?", Good questions involve "I walked 10 miles but the environment looks the same, can someone come pick me up?"

gerryg400 wrote:Did you do an

Code: Select all

fninit

on the ap core

matute81 wrote:

gerryg400 wrote:Did you do an

Code: Select all

fninit

on the ap core

Sure!
The strangest thing is that the status word after initialization is not 0, like it should be after a fninit instruction (and like it is on BSP core). There must be something wrong in AP's FPU initialization but I'm not able to find what

So I asked some help here...not because I don't want to resolve it myself!

matute81 wrote:@Cjreek:
nasm assembly:

Code: Select all

FUNCTION SysFpuInit
  push eax
  mov  eax, cr0
  and  eax, 0xfffffffb
  or   eax, 0x22
  mov  cr0, eax
  clts
  pop  eax
  ret
ENDFUNC SysFpuInit

matute81 wrote:Dear Combuster,
I post a question about this because is incomprehensible for me why a code that works on one core don't works for other core. If you can't or don't want to explain me why I have a stack overflow when I assign a value to a floating point variable no problem, but don't give me a life lesson ok? I'm searching for answers not unuseful lessons.
Thank you anyway