[ros-dev] Save FPU on task switch/SSE support

[Hartmut Birr]

> -----Original Message-----
> From: ros-dev-bounces at reactos.com 
> [mailto:ros-dev-bounces at reactos.com] On Behalf Of Alex Ionescu
> Sent: Friday, October 08, 2004 11:48 PM
> To: ReactOS Development List
> Subject: Re: [ros-dev] Save FPU on task switch/SSE support
> 
> 
> Hi,
> 
> As I added the KPRCB I noticed the last field is called 
> NpxSaveArea and 
> contains the last FPU/SSE state, iirc.
> 
> You might want to save it there...but what troubles me is 
> that the KPRCB 
> is a CPU-wide structure, not thread-limited.
> 

For each thread we need two save areas (user and kernel mode) because win32k
and free type are using the fpu. This is different to Windows. On a callback
from kernel to user mode we need more than this two save areas for a thread.
The save area in the kpcr structure is for entering/leaving the standby
mode.

- Hartmut