RE: [ros-dev] Re: [ros-diffs] [CVS reactos] - Saved the state of the fpu at a win32 call and restored the state

[Hartmut Birr]

Hi,

I've made this changes, because syssetup does always crash ros in
KiHandleFpuFault line #462 on my smp machine. The crash is triggered from
fxsave in tskswitch.S after a win32 callback. I revert my changes.

- Hartmut  

>   -----Original Message-----
>  From: ros-dev-bounces(a)reactos.com 
>  [mailto:[e-mail]] On Behalf Of Gregor Anich
>  Sent: Saturday, November 27, 2004 10:57 PM
>  To: ReactOS Development List
>  Subject: [ros-dev] Re: [ros-diffs] [CVS reactos] - Saved the 
>  state of the fpu at a win32 call and restored the state
>  
>  
>  Hi Hartmut!
>  
>  You have changed the w32 callback to save the FPU state, this 
>  is wrong I 
>  think!
>  I was wondering too wether it should be saved so GvG 
>  suggested to check 
>  myself and I modified our winhello app...
>  It prints out the FPU control word, calls CreateWindow and printf the 
>  FPU control word again.
>  In the callback for the WM_CREATE message (produced by 
>  CreateWindow) it 
>  also prints the control word, then modifies it (and prints 
>  the modified one)
>  
>  This is the output on windows2000:
>  Original FPU control word: 0x8001f
>  WM_CREATE: Original FPU control word: 0x8001f
>  WM_CREATE: Modified FPU control word: 0xa001f
>  FPU control word after CreateWindow: 0xa001f
>  
>  Of course I have attached the program.
>  
>  I am not sure but I think in the KiClearFloatingPointState which you 
>  have added you have to set KPCR->NpxThread to NULL if it's 
>  CurrentThread 
>  before you do the fn/xsave because it could raise a delayed FPU 
>  exception (which will be ignored when KPCR->CurrentThread is 
>  NULL and be 
>  delivered when the saved FPU state is restored for the thread)
>  
>  I think I have made the same mistake in tskswitch.S - I am 
>  pretty sure 
>  it has to be fixed there because we don't want a FPU exception to be 
>  raised while we are in a cli/sti block and switching to another task.
>  
>  - blight
>